Applied Chemistry.pptx

Applied Chemistry Up to Four Chapters.

1. Applied Chemistry Course outline: Physical Chemistry : Properties of various groups and periods of periodic table. Atomic Structure and Interatomic bonding : Atomic structure, atomic bonding and mechanical bonding. Polymorphism and allotropic forms. Crystallography basics. Basic Mechanical properties : Structure of metals and ceramics. Thermo-chemistry : Chemical Thermodynamics, Hess’s Law, heat of Formation and reaction, relation between H and U, measurement of heat reaction, Bomb calorimeter Electrochemistry : Laws of electrolysis Industrial Chemistry : Industrial chemistry introduction, manufacturing and uses of various hydrocarbons. Lubricants and oils. Production and application of paints, vulcanized rubber and fuels. Environmental pollution and control. Water Treatment Methods : Water softening, treatment of water for industrial purposes.

2. Applied Chemistry Assessment: Mid Term, Presentation, Assignments, Quizzes, Report Writing, Final Term Text and Reference books: W. H. Brown and L. S. Brown, Chemistry for Engineering Students , Cengage Learning, 3 rd ed. O. V. Roussak , H. D. Gesser , Applied Chemistry: A Textbook for Engineers and Technologists: Springer. S. S. Zumdahl , Chemistry: An Atoms First Approach , Cengage . N. J. Tro , Chemistry: A Molecular Approach, Pearson. M. J. Shultz, Engineering Chemistry , Cengage . Bahl , B. S. Bahl , G. D. Tuli , Essential of Physical Chemistry , S. Chand Publishing, India.

3. Applied Chemistry Definition: Applied Chemistry is the scientific field for understanding basic chemical properties of materials and for producing new materials with well-controlled functions. It has four areas of study: physical chemistry, materials chemistry, chemical engineering, and environmental chemistry Examples of applied chemistry include creation of the variety of laundry detergents on the market and development of oil refineries Physical Chemistry: is the study of macroscopic, and particulate phenomena in chemical systems in terms of the principles, practices, and concepts of physics such as motion, energy, force, time, thermodynamics, quantum chemistry, statistical mechanics, analytical dynamics and chemical equilibrium. Materials Chemistry: is the section of Materials Science and Engineering that investigates the chemical nature of materials. ... The diverse nature of materials arises from their atomic composition and their complex molecular structures, which are organized over many different length scales.

4. Applied Chemistry Chemical engineering: is a certain type of engineering which deals with the study of operation and design of chemical plants as well as methods of improving production. Chemical engineers develop economical commercial processes to convert raw material into useful products . Environmental chemistry : is  the study of chemical processes that occur in water, air, terrestrial and living environments, and the effects of human activity on them. It includes topics such as astrochemistry , atmospheric chemistry, environmental modelling, geochemistry, marine chemistry and pollution remediation.

5. Atomic Structure and Interatomic bonding: Fundamental Concepts of the Atom Our current model of the structure of atoms has been accepted for nearly a century, but it took great creativity and many ingenious experiments to develop. The atom is composed of a small, compact core called the nucleus surrounded by a disperse cloud of electrons . The nucleus is composed of two types of particles: protons and neutrons . There is so much space between the electrons and the nucleus that it is impossible to show it to scale in an illustration. Consider the figure which show the relative positions of the protons, neutrons, and electrons. But if the protons and neutrons were actually the size shown, then the electrons would be hundreds of meters away. Another misunderstanding promoted by this type of illustration is the picture of electrons following regular orbits around the nucleus. A better model of atomic structure views the electrons as clouds of negative charge that surround the nucleus, as opposed to particles that orbit around it in an orderly way (Figure (b )).

6. Atomic Structure and Interatomic bonding:

7. Atomic Structure and Interatomic bonding: Now we turn our attention to the numbers of protons, neutrons, and electrons in the atom. Electric charge provides an important constraint on these numbers. Protons are positively charged, electrons are negatively charged, and neutrons are neutral. Atoms themselves are also electrically neutral, so the numbers of protons and electrons present must be such that their charges will cancel each other. You may know from physics that the SI unit of charge is the coulomb (C). Experiments have shown that the electrical charges on a proton and an electron are equal and opposite. Every electron carries a charge of −1.602 × 10−19 C, whereas every proton carries a charge of +1.602 × 10−19 C. So for an atom to remain neutral, the numbers of electrons and protons must be equal. Because neutrons have no charge, the number of neutrons present is not restricted by the requirement for electrical neutrality. For most elements, the number of neutrons can vary from one atom to another, as we’ll see.

8. Atomic Structure and Interatomic bonding: Atomic Number and Mass Number The number of protons in a particular atom, referred to as the atomic number, identifi es the element. The atomic number of carbon is six, which tells us that a neutral carbon atom has six protons. Electrical neutrality requires that a carbon atom also must have six electrons. The great majority of carbon atoms—roughly 99%—also contain six neutrons. But some carbon atoms contain seven or even eight neutrons. Atoms of the same element that have different numbers of neutrons are called isotopes. Protons and electrons govern nearly all of the important chemical properties of atoms, so generally isotopes cannot be separated chemically. But the existence and even the relative abundance of isotopes can be proven by careful examinations of the mass of atoms. Protons and neutrons have similar masses; each is nearly 2000 times more massive than the electron. So the mass of any atom is concentrated in its nucleus. Individual atoms are so small and light that reporting their masses in conventional units such as kilograms or grams is not convenient.

9. Atomic Structure and Interatomic bonding: Atomic Number and Mass Number Instead we use a unit that is appropriate to the atomic scale: the atomic mass unit or amu . 1 amu = 1.6605 × 10−24 g Both the neutron and the proton have masses very close to one amu . The mass of a neutron is 1.009 amu , and that of a proton is 1.007 amu . The mass of an electron, in contrast, is just 0.00055 amu . So for many practical purposes, we can determine the mass of an atom simply by counting the number of protons and neutrons. That number will be the mass in amu , to a fairly reasonable approximation. Because of this, the combined total of protons and neutrons is called the mass number of the atom. Because isotopes are atoms of the same element with different numbers of neutrons, they will have the same atomic number but different mass numbers.

10. Atomic Structure and Interatomic bonding: Isotope: are two or more types of atoms that have the same  atomic number  (number of  protons  in their  nuclei ) and that differ in  nucleon  numbers ( mass numbers ) due to different numbers of  neutrons  in their nuclei. While all isotopes of a given element have almost the same chemical properties, they have different atomic masses and physical properties. The term isotope is formed from the Greek roots isos (" equal") and topos ("place "), meaning "the same place"; thus, the meaning behind the name is that different isotopes of a single element occupy the same position on the  periodic table .   The number of protons within the  atom's nucleus  is called  atomic number  and is equal to the number of  electrons  in the neutral (non-ionized) atom. Each atomic number identifies a specific element, but not the isotope; an atom of a given element may have a wide range in its number of  neutrons . The number of  nucleons  (both protons and neutrons) in the nucleus is the atom's  mass number , and each isotope of a given element has a different mass number. For example,  carbon-12 ,  carbon-13 , and  carbon-14  are three isotopes of the element  carbon  with mass numbers 12, 13, and 14, respectively. The atomic number of carbon is 6, which means that every carbon atom has 6 protons so that the neutron numbers of these isotopes are 6, 7, and 8 respectively.

11. Atomic Structure and Interatomic bonding: Atomic Symbols All the information about the structure of the atom, which we have just discussed, can be written in scientific shorthand, using atomic symbols. The general atomic symbol can be written as Here E represents the atomic symbol for the element in question, the superscript A is the mass number, and the subscript Z is the atomic number. The symbol for carbon-12, for example, is . Many atomic symbols are fairly obviously derived from the name of the element, such as the use of C for carbon in our example. For other elements, the symbol is based on the Latin name. The symbol for iron, for example, is Fe , derived from the Latin name ferrum . An atom of iron with 26 protons and 30 neutrons is represented as . A full list of elements and their symbols can be found in periodic Table.  

12. Atomic Structure and Interatomic bonding: Atomic Masses The atomic mass is defined as the average mass of an atom of a particular element.Carbon has two stable isotopes with masses of 12.0000 and 13.0036 amu , respectively . So why is the average mass 12.011 and not something closer to 12.5? The answer is that when we take the average mass, we must account for the relative abundance of each isotope. Suppose that we could measure the mass of a 100-atom sample . Based on the isotopic abundances, we would expect to have 99 atoms of carbon-12 and only a single atom of carbon-13. In any sample that we can actually weigh , the number of atoms will be far greater than 100. Even using the best available laboratory balances, the smallest quantity of matter that can be weighed is about a nanogram , or 10−9 g. A nanogram of carbon would contain more than 1013 atoms . For such large numbers of atoms, it is safe to assume that the fraction of each isotope present will be determined by the natural abundances. For carbon, the fact that we only need to consider two stable isotopes makes the calculation fairly simple. We can multiply the mass by the fractional abundance to weight each isotope’s contribution to the atomic mass. Carbon-12 : 12.0000 × 0.9893 = 11.87, Carbon-13: 13.0036 × 0.0107 = 0.139 Weighted average mass = 11.87 + 0.139 = 12.01 , The value of 12.011 found in the periodic table is obtained using additional significant figures on the isotopic abundance numbers.

13. Atomic Structure and Interatomic bonding: Atomic Masses EXAMPLE PROBLEM 2.1 ( Polyvinyl chloride) The chlorine present in PVC has two stable isotopes. 35Cl with a mass of 34.97 amu makes up 75.77% of the natural chlorine found. The other isotope is 37Cl, whose mass is 36.95 amu . What is the atomic mass of chlorine? Strategy To determine the atomic mass, we must calculate the average mass weighted by the fractional abundance of each chlorine isotope. Because there are only two stable isotopes, their abundances must add up to 100%. So we can calculate the abundance of 37Cl from the given abundance of 35Cl. Solution First, we calculate the abundance of the chlorine-37 isotope: Abundance of 37Cl = 100% − 75.77% = 24.23% Now we can calculate the contribution of each isotope to the atomic mass. 35Cl: 34.97 × 0.7577 = 26.50, 37Cl : 36.95 × 0.2423 = 8.953 Weighted average mass = 26.50 + 8.953 = 35.45, So the atomic mass of chlorine is 35.45 amu .

14. Ions: Ions A ny atom or group of atoms that bears one or more positive or negative electrical charges is called Ion. Positively charged  ions  are called cations The charge of the  electron  is considered negative by convention. The negative charge of an electron is equal and opposite to charged  proton (s) considered positive by convention. The net charge of an ion is not zero due to its total number of electrons being unequal to its total number of protons. Ions can also play important roles in many chemical processes, including several that are important in the large-scale production of polymers . When an ion is derived from a single atom it is called a monatomic ion. When groups of atoms carry a charge they are called polyatomic ions. Monatomic or polyatomic ions may carry either negative or positive charges. Negatively charged ions are called anions, and they contain more electrons than protons. Similarly, an ion with more protons than electrons has a positive charge and is called a cation . T wo fundamental aspect about electric charge are: First, opposite charges attract each other and like charges repel one another. And second, electric charge is conserved. These two ideas have important implications for the formation of ions in chemical processes.

15. Ions: Ions- Mathematical Description The statement that “opposites attract and likes repel” can be quantified mathematically . Coulomb’s law , describes the interaction of charged particles. The attraction of opposite charges and the repulsion of like charges are both described mathematically by one simple equation : Here q 1 and q 2 are the charges, is a constant called the permittivity of a vacuum, and r is the distance between the charges. F is the force the objects exert on one another as a result of their charges. When both charges have the same sign—either positive or negative—the resultant value for the force is a positive number . When the charges are opposite, the value is negative. This is consistent with the usual sign conventions used for force and energy ; a negative value of F indicates an attractive force and a positive value a repulsive one . Now consider the effect of varying the distance, r , between two ions. If two positively charged particles are initially very far apart (effectively infinite distance), the r 2 term in the denominator of Equation will be very large. This in turn means that the force F will be very small, and so the particles will not interact with each other significantly . As the two like charges are brought closer together, the r 2 term in the denominator shrinks and so the (positive) force grows larger: the particles repel each other . If we somehow force the particles closer together, the repulsive force will continue to grow .

16. Ions: Ions and Their Properties : Many monatomic cations and anions exist. These ions can exist in the gas phase, and many are important in atmospheric chemistry. But we encounter ions most frequently when dealing with the chemistry of substances dissolved in water. For example, sodium atoms lose an electron relatively easily to form the sodium cation , Na+. Because it still has 11 protons, this ion retains the symbol of sodium, yet it does not behave at all like an atom of sodium. Consider an order of French fries. You may have heard news stories about the high amount of sodium in an order of fries, and concerns have been raised about the possible health effects of too much sodium in our diets. This statement could be confusing because here the word “sodium” does not refer to sodium metal . In fact, if we place sodium metal on freshly made French fries, the metal will burst into flame ! The sodium we hear about in stories on diet and health is actually sodium ion, which is added to the fries when salt is sprinkled on. Too much salt might still be a health concern, but we certainly don’t worry about the salt igniting . There is a big difference between ions and atoms, at least in this case . In contrast to sodium, chlorine readily gains an extra electron forming the chloride ion Cl −. Again, there is a noticeable difference between the ion and the atom of chlorine. The table salt we discussed above is sodium chloride, which contains chloride anions . Just like sodium, these chloride ions are present in French fries or any other salted foods. Chlorine atoms, on the other hand, combine in pairs to form a yellowish-green gas, Cl2, which irritates the lungs and can be toxic. The behavior of the ion is clearly much different from that of the neutral atom or molecule.

17. Compounds and Chemical Bonds: Chemical Formulas: A chemical compound is a pure substance made up of atoms of two or more elements joined together by chemical bonds. In any compound, the atoms combine in fixed whole number ratios. In any such combination, the resultant substance behaves differently from the atoms alone. In many compounds, atoms combine to form discrete particles called molecules . Molecules can be broken down into their constituent atoms , but the resulting collection of atoms no longer behaves like the original molecule . Other materials are composed of vast arrays or extended structures of atoms or ions but do not form discrete molecules. Alloys, metals, and ionic solids (composed of paired ions) fall into this category of chemical compounds. We’ve seen how we can use atomic symbols as shorthand notation to designate atoms. That same idea can be extended to describe the composition of either molecules or extended compounds in a simple symbolic repre sentation. A chemical formula describes a compound in terms of its constituent elements . We will actually encounter two distinct types of chemical formulas: molecular formulas and empirical formulas. The molecular formula of a compound is a kind of parts list that describes the atomic composition of a molecule efficiently . The molecular formula of the ethylene (colorless flammable gas) monomer from which polyethylene is produced is C2H4 ; this tells us that there are two carbon atoms and four hydrogen atoms per molecule. The empirical formula tells us only the relative ratio between the numbers of atoms of the

18. Compounds and Chemical Bonds: different elements present. Let’s consider ethylene again. The ratio of carbon atoms to hydrogen is 1:2. So the empirical formula is CH2. When dealing with an empirical formula, it is important to realize that it does not tell how large or small an individual molecule of the compound might be; only the relative numbers of atoms of each element are given. We often emphasize this fact by writing a subscript ‘ n ’ on the entire formula. For ethylene, this would give us (CH2) n , which means that each molecule must contain some integral number of CH2 units. There are four rules that allow us to write most formulas: 1 . Indicate the types of atoms in the substance by their atomic symbols. 2. The number of each atom in the compound is indicated by a subscript to the right of the atomic symbol. For example, the chemical formula of ethylene, C2H4, tells us that each molecule contains two carbon atoms and four hydrogen atoms. 3. Groups of atoms can be designated by using parentheses. Subscripts outside these parentheses mean that all atoms enclosed in the parentheses are multiplied by the value indicated in the subscript. 4. Water molecules associated with certain compounds called hydrates are indicated separately from the rest of the compound.

19. Compounds and Chemical Bonds: Chemical Bonding Atoms combine to make compounds by forming chemical bonds. Several different types of chemical bonds are possible, and once we learn to recognize them, these types of bonds will help us to understand some of the chemical properties of many substances . All chemical bonds share two characteristics. First, all bonds involve exchange or sharing of electrons. Second , this exchange or sharing of electrons results in lower energy for the compound relative to the separate atoms . A chemical bond will not form, or will have only a temporiry existence, unless it lowers the overall energy of the collection of atoms involved. Chemical bonds can be divided into three broad categories: ionic, covalent, and metallic. Some compounds are composed of collections of oppositely charged ions that form an extended array called a lattice . The bonding in these compounds is called ionic bonding . To form the ions that make up the compound, one substance loses an electron to become a cation , while another gains an electron to become an anion. We can view this as the transfer of an electron from one species to another. ionic compound, NaCl . Ionic compounds form extended systems or lattices of alternating positive and negative charges. Although the formula NaCl correctly indicates that sodium and chlorine are present in a 1:1 ratio, we cannot really identify an individual “molecule” of NaCl . To emphasize this

20. Compounds and Chemical Bonds: Chemical Bonding distinction , we sometimes refer to a formula unit , rather than a molecule, when talking about ionic compounds. The formula unit is the smallest whole number ratio of atoms in an ionic compound.

21. Compounds and Chemical Bonds: Chemical Bonding Metals represent another type of extended system, but here the chemical bonding is totally different. In metals, the atoms are once again arranged in a lattice, but positively and negatively charged species do not alternate. Instead, the nuclei and some fraction of their electrons comprise a positively charged “core” localized at these lattice points, and other electrons move more or less freely throughout the whole array . This is called metallic bonding . Metallic bonding leads to electrical conductivity because electrons can move easily through the bulk material. Figure shows a schematic illustration of the concept of metallic bonding .

22. Compounds and Chemical Bonds: Chemical Bonding When electrons are shared between pairs of atoms rather than donated from one atom to another or mobile across an entire lattice, we have covalent bonds . In covalent bonds , electrons are usually shared in pairs. Two electrons (and sometimes four or six) are located between two nuclei and the sharing leads to an attraction between the nuclei. The long chains in all polymers are formed by covalent bonds in which electrons are shared between adjacent carbon atoms.

23. The Periodic Table : One of the most recognizable tools of chemistry is the periodic table. Periodic table summarizes a wealth of information about the behavior of elements, organizing them simultaneously in ascending order of atomic number and in groups according to chemical behavior. An experienced chemist can get a rough idea of an element’s properties simply from where that element sits in the periodic table . Russian scientist Mendeleev had published his first periodic table and enumerated the periodic law : when properly arranged, the elements display a regular and periodic variation in their chemical properties . The most significant and impressive feature of Mendeleev’s work was his prediction of the existence of undiscovered elements. He left holes in his proposed table at positions where no known element seemed to fi t. Later, when the elements to fill in these holes were identified , the scientific community accepted Mendeleev’s work. The discovery of the periodic law and construction of the periodic table represents one of the most significant creative insights in the history of chemistry. Prior to Mendeleev’s time, chemists had to learn the properties of each element individually. As more and more elements were discovered, that task became increasingly difficult. The periodic table helped the study of chemistry to expand quickly by providing a simple, visual means to organize the elements in terms of their chemical and physical properties.

24. The Periodic Table : Periods and Groups The modern periodic table simultaneously arranges elements in two important ways: the horizontal rows of the table, called periods , and the vertical columns, called groups . The term “period” is used for the rows because many important properties of the elements vary systematically as we move across a row. Figure shows a plot of the density of elements, all in their solid state, as a function of atomic number . From the graph, it is clear that density varies according to a fairly regular pattern that goes through a series of minima and maxima. Different colors are used for the data points in this graph to show how the variation in density is correlated with position in the periodic table. Each color represents a period (row) in the table. Because the elements in the periodic table are arranged in order of increasing atomic number , moving across each segment of the graph corresponds to moving from left to right across the corresponding row of the periodic table. You can see readily that as we move across a row in this way, the density of the elements is initially small, increases until passing through a maximum, and then decreases again. 2 nd figure shows the same data, with the density represented by the shading of each element’s box. This representation clearly shows how the density of the elements varies regularly across each row of the table. The rows in the table are numbered 1 through 7 sequentially from top to bottom.

25. The Periodic Table : Periods and Groups

26. The Periodic Table : Periods and Groups Although the properties of the elements can vary widely across a period, each column collects elements that have similar chemical properties. Most elements can combine with hydrogen to form compounds. The graph in Figure shows the number of hydrogen atoms with which an atom of each element will combine, and the regular variation in the plot clearly shows that this is a periodic property. Elements in a group (column) combine with the same number of hydrogen atoms. Fluorine, chlorine , and bromine each combine with one atom of hydrogen, for example, and all fall in the same group. These types of chemical similarities were among the evidence that led to the development of the periodic table, so some of the groups predate the general acceptance of the table. These groups of elements were assigned names and those names have remained with them. Thus the elements in the far left-hand column (Li, Na, K, Rb , and Cs) are known collectively as alkali metals . Similarly, Be, Mg, Ca , Sr , and Ba are called alkaline earths , and F, Cl , Br, and I are referred to as halogens . He, Ne, Ar , Kr , and Xe were discovered much later than most of the other elements, and they have been named rare gases or noble gases . Other groups are named, but their names are less commonly used and won’t be mentioned here.

27. The Periodic Table : Periods and Groups There are also names for different regions of the table. Elements in the two groups on the left side of the table and the six groups on the right side are collectively referred to as representative elements , or main group elements . Elements that separate these two parts of the representative groups in the main body of the periodic table are called transition metals . Iron is an example of a transition metal . The elements that appear below the rest of the periodic table are called lanthanides ( named after the element lanthanum, Z = 57) and actinides (named after the element actinium , Z = 89 ). In addition to these names, several numbering systems have been used to designate groups . Current convention dictates numbering from left to right starting with 1 and proceeding to 18. Thus, for example, the group containing C, Si, Ge , Sn , and Pb is referred to as Group 14.

28. The Periodic Table : Metals, Nonmetals, and Metalloids Another way to classify an element is as a metal , nonmetal , or metalloid . Once again , the periodic table conveniently arranges elements so that one can place a given element easily into one of these categories .

29. The Periodic Table : Metals, Nonmetals, and Metalloids Most of the elements are metals. Their general location in the periodic table is toward the left and bottom, as seen in the coloring of the periodic table in Figure Metals share a number of similarities in chemical and physical properties. Physically , metals are shiny, malleable, and ductile (meaning they can be pulled into wires). They also conduct electricity, so wires are always made from metals. Chemical properties can also be used to distinguish metals. Metallic elements tend to form cations in most of their compounds. Nonmetals occupy the upper right-hand portion of the periodic table. There are fewer nonmetals than metals. But when we consider the relative importance of elements , nonmetals hold their own because of their role in the chemistry of living things . Most of the molecules that make up the human body consist predominantly or exclusively of the nonmetallic elements carbon, hydrogen, oxygen, nitrogen, sulfur , and phosphorus. As our examples so far might lead you to guess, polymers also consist almost exclusively of nonmetallic elements. In contrast to metals, nonmetals are not shiny , malleable, or ductile nor are they good conductors of electricity. These physical properties provide one means by which we can distinguish metals from nonmetals. Whether an element is a metal or nonmetal may seem simple to determine based

30. The Periodic Table : Metals, Nonmetals, and Metalloids on the physical properties cited above. Yet, some elements cannot be classified easily as either metal or nonmetal. The question whether or not a substance conducts electricity, for example, does not always have a simple yes or no answer. Lacking a reliable means of drawing a clean boundary between the two categories, scientists have generally chosen to refer to intermediate cases as metalloids or semimetals . In the periodic table, metalloids are clustered along a diagonal path, as shown in Figure.

31. Inorganic and Organic Chemistry: Just as engineering can be broken down into various specialties, so too, chemistry can be viewed as a collection of subfields . Two of the most fundamental areas of chemistry are organic chemistry and inorganic chemistry . These names arise from the fact that at one time organic chemistry would have been defined as the chemistry of living things. A more modern definition is that organic chemistry is the study of compounds of the element carbon. As we’ve already seen, this includes naturally occurring biological molecules and also nearly all synthetic polymers. Inorganic chemistry is the study of all other elements and their compounds. Inorganic Chemistry: Many inorganic compounds exist as relatively small molecules whose atoms are joined together through covalent bonds. One such compound is silicon tetrachloride, SiCl4, which has important uses in the production of semiconductors. Four chlorine atoms surround a central silicon atom, and each chlorine shares one pair of electrons with the silicon. Silicon and chlorine are both main group elements, found in Groups 14 and 17 of the periodic table, respectively. As mentioned, elements from the same group tend to display similar chemical properties.

32. Inorganic and Organic Chemistry: Inorganic Chemistry and Transition Metals : Thus once we know that SiCl4 exists , we might expect that other pairs of elements from the same groups might form similar compounds. And this prediction is correct: compounds such as SnCl4 and CF4 do exist and have structures and bonds analogous to SiCl4. Other compounds of the main group elements form extended ionic structures , such as that of NaCl . But despite the difference in the types of chemical bonds employed, we can still readily predict that similar compounds should exist for other pairs of elements from the same groups. From the periodic table, we see that sodium is in Group 1 and chlorine is in Group 17. So we can expect that other pairs of elements from these columns of the table will form ionic solids, too. Again, our prediction is accurate; compounds such as LiCl , NaF , and KBr have structures analogous to that of NaCl . The reason for the existence of these similar compounds is simple . All of the metals in Group 1 form cations with a 1+ charge, and all of the elements in Group 17 form anions with a 1− charge. Any of these cations can combine with any of the anions in a 1:1 ratio to form neutral compounds .

33. Inorganic and Organic Chemistry: Inorganic Chemistry and Transition Metals : The chemistry of transition metals is somewhat more complicated than that of the main group elements, though, because most transition metals can form multiple cations with different charges. Iron commonly forms two different monatomic cations : Fe2+ and Fe3+. As a result of this, iron can form a more diverse set of compounds than Group 1 metals. It can combine with chlorine to form either FeCl2 or FeCl3, and these two compounds have significantly different physical properties. Largely because they can form multiple cations , the chemistry of transition metals does not vary as sharply from group to group. Regardless of their positions in the periodic table , for example, most transition metals can form cations with a 2+ charge. Thus predictions based simply on group number are not as reliable here as they are for the representative elements . When considering transition metals and their compounds, we must rely more heavily on knowledge of the specific chemistry of each element.

34. Inorganic and Organic Chemistry: Inorganic Chemistry and Transition Metals : The chemistry of transition metals is somewhat more complicated than that of the main group elements, though, because most transition metals can form multiple cations with different charges. Iron commonly forms two different monatomic cations : Fe2+ and Fe3+. As a result of this, iron can form a more diverse set of compounds than Group 1 metals. It can combine with chlorine to form either FeCl2 or FeCl3, and these two compounds have significantly different physical properties group 3 to group 12.

35. Inorganic and Organic Chemistry: Organic Chemistry: By definition, an organic compound is based on carbon atoms. So to reduce clutter in a line drawing , the ‘C’ symbols for carbon atoms are not written. Furthermore, because organic compounds almost always contain many hydrogen atoms, the ‘H’ symbol for any hydrogen atom that is attached directly to a carbon atom is also not written. Symbols are written for any elements other than carbon and hydrogen, as well as for any hydrogen atoms that are not directly attached to carbon. Poly(methyl methacrylate) is widely known as Plexiglas®. The structural formula for the monomer, methyl methacrylate, is shown below. Write the corresponding line structure for methyl methacrylate.

36. Chemical Nomenclature: Although only a limited number of elements exist, the number of compounds that may be formed from those elements is virtually boundless. Given the vast number of molecules that can be made, we require a systematic means of assigning names to chemical compounds. This system should be sufficiently well defined that a person who knows the rules can draw the structure of any compound, given its systematic name . This naming process for molecules is often referred to as chemical nomenclature . Binary Systems Compounds that contain only two elements are called binary compounds . Fe2O3, for example, is a binary compound . Different rules exist for naming binary molecules held together by covalent bonds and ionic compounds . When two nonmetals combine, they usually form a covalent compound . But when metals and nonmetals combine with one another, they frequently form ionic compounds. Naming Covalent Compounds In some cases, a given pair of elements can form compounds in a number of different ways . Nitrogen and oxygen, for example, form NO, N2O, NO2, N2O3, N2O4, and N2O5 , all of which are stable enough to observe. So it is critical that our naming system distinguishes

37. Chemical Nomenclature: these different molecules. To accomplish this, the nomenclature system uses a prefix to specify the number of each element present. The first ten of these prefixes , which arise from the Greek roots for the numbers, are listed in Table In a binary compound, the element that appears first in the formula also appears first in the name . The first element retains its full name , whereas the second element is described by replacing the ending from its name with the suffix -ide . Both elements will be preceded by a number-designating prefix except that when there is only one atom of the first element , it does not carry the prefix mono- .

38. Chemical Nomenclature: EXAMPLE What are the systematic names of the following compounds? (a) N2O5, (b) PCl3 , ( c) P4O6? Solution (a) N2O5: dinitrogen pentoxide , (b) PCl3: phosphorus trichloride ( remember : this is not called mono phosphorus trichloride ), (c) P4O6: tetraphosphorus hexoxide . ( The a in hexa - is dropped here to simplify pronunciation .) Naming Ionic Compounds T he name of a monatomic cation is simply the name of the element followed by the word   ion . Thus, Na +  is the sodium ion, Al 3+  is the aluminum ion, Ca 2+  is the calcium ion, and so forth . We have seen that some elements lose different numbers of electrons, producing ions of different charges. Iron, for example, can form two cations , each of which, when combined with the same anion, makes a different compound with unique physical and chemical properties. Thus, we need a different name for each iron ion to distinguish Fe 2+  from Fe 3+ . The same issue arises for other ions with more than one possible charge.

39. Chemical Nomenclature: There are two ways to make this distinction. In the simpler, more modern approach, called the  Stock system , an ion’s positive charge is indicated by a roman numeral in parentheses after the element name, followed by the word  ion . Thus, Fe 2+  is called the iron(II) ion, while Fe 3 +  is called the iron(III) ion. This system is used only for elements that form more than one common positive ion. We do not call the Na +  ion the sodium(I) ion because (I) is unnecessary . Sodium forms only a 1+ ion, so there is no ambiguity about the name  sodium ion . The second system, called the  common system , is not conventional but is still prevalent and used in the health sciences. This system recognizes that many metals have two common cations . The common system uses two suffixes (- ic  and - ous ) that are appended to the stem of the element name. The  - ic  suffix represents the greater of the two cation charges, and the  - ous  suffix represents the lower one. In many cases, the stem of the element name comes from the Latin name of the element . The name of a monatomic anion consists of the stem of the element name, the suffix - ide , and then the word  ion . Thus, as we have already seen, Cl −  is “ chlor -” + “-ide ion,” or the chloride ion. Similarly, O 2−  is the oxide ion, Se 2−  is the selenide ion, and so forth

40. Chemical Nomenclature: Element Stem Charge Modern Name Common Name iron ferr- 2+ iron(II) ion ferrous ion 3+ iron(III) ion ferric ion copper cupr- 1+ copper(I) ion cuprous ion 2+ copper(II) ion cupric ion tin stann- 2+ tin(II) ion stannous ion 4+ tin(IV) ion stannic ion lead plumb- 2+ lead(II) ion plumbous ion 4+ lead(IV) ion plumbic ion chromium chrom- 2+ chromium(II) ion chromous ion 3+ chromium(III) ion chromic ion gold aur- 1+ gold(I) ion aurous ion 3+ gold(III) ion auric ion Ion Name F − fluoride ion Cl − chloride ion Br − bromide ion I − iodide ion O 2− oxide ion S 2− sulfide ion P 3− phosphide ion N 3− nitride ion

41. Chemical Nomenclature: Many compounds contain polyatomic anions,. Most often, the names of these polyatomic ions are memorized rather than being obtained by a systematic nomenclature rule. There is, however, a system for polyatomic anions that contain oxygen and one other element, oxyanions . The base name of the oxyanion is provided by the element that is not oxygen. If there are two possible groupings of the element with oxygen, the one with more oxygen atoms uses the suffix -ate and the one with fewer oxygens uses the suffix - ite . When there are four possible oxyanions, we add a prefix per- to the -ate suffix for the most oxygens and a prefix hypo- to the - ite suffix for the least oxygens . Chlorine is the classic example of an element that forms four oxyanions, whose names are provided in Table Once we know how to name both of the ions, an ionic compound is named simply by combining the two names. The cation is listed fi rst in the formula unit and in the name.

42. Chemical Nomenclature:

43. The Periodic Table and Atomic Structure The relationship between the electron configuration predicted by the quantum mechanical model of the atom and the periodic table was vital to the acceptance of quantum mechanics as a theory. The coloring of regions in this figure divides the table into four blocks of elements. The elements in each block are similar in that the electron in the highest energy orbital comes from the same subshell. Thus all the elements in the section at the left edge of the table, shaded in red, have their highest energy electron in an

44. The Periodic Table and Atomic Structure orbital . These are sometimes referred to as the s block. The green section at the far right of the table is the p block because according to the aufbau principle, the last orbital occupied is a p orbital. The transition metals are d -block elements (shown in purple), and the lanthanides and actinides make up the f block (shown in yellow). Because of this structure, we can use the periodic table to determine electron configurations for most elements. (A few exceptions arise, mainly among the transition metals.) We find the element of interest in the periodic table and write its core electrons using the shorthand notation with the previous rare gas element. Then we determine the valence electrons by noting where the element sits within its own period in the table .

45. The Periodic Table and Atomic Structure Electronic Configuration

46. 2 nd Chapter Polymorphism “Poly” means many and “ morphism ” means forms or shaps . The word polymorphism means having many forms. Polymorphism is  the ability of an object to take on many forms .... Real life example of polymorphism:  A person at the same time can have different characteristic . Like a man at the same time is a father, a husband, an employee. So the same person posses different behavior in different situations. This is called polymorphism. In the crystallographic context, crystal polymorphism, refers  to the ability of a certain compound to exist in different crystallographic structures, resulting from different packing arrangements of its molecules in the crystal structure polymorphism , in crystallography, the condition in which a  solid   chemical compound  exists in more than one crystalline form; the forms differ somewhat in physical and, sometimes, chemical properties, although their solutions and vapours are identical. Polymorphism and allotropic forms. Crystallography basics

47. Allotropic The existence of different crystalline or molecular forms of elements is called  allotropy , although it has been suggested that the meaning of allotropy should be restricted to different molecular forms of an element, such as oxygen (O 2 ) and ozone (O 3 ), and that polymorphism be applied to different crystalline forms of the same species, whether a  compound  or an element. Differences in the crystalline forms of many elements and  compounds  were discovered during the 1820s Among polymorphs of certain compounds, one is more stable than the others under all conditions; in the cases of other compounds, one polymorph is stable within a particular range of temperature and pressure while another is stable under a different set of conditions. In either circumstance, the rate at which a less stable polymorph becomes more stable often is so low that an intrinsically unstable form may persist indefinitely. As an example of the first class,  calcium carbonate  has an orthorhombic form ( i.e.,  having three unequal crystalline axes at right angles to each other) called  aragonite  and a Polymorphism and allotropic forms. Crystallography basics

48. hexagonal form (having three equal axes intersecting at angles of 60 degrees and a fourth  axis  at right angles to these three) called  calcite . Calcite is the stabler form; aragonite changes into calcite rapidly at temperatures around 470° C (about 880° F) but very slowly at room temperatures. The second class is represented by  silica , which has three forms—quartz, tridymite , and cristobalite —each of which is stable only in its particular range of temperature and pressure, the others slowly changing into the stable modification. Hexagonal Cube Polymorphism and allotropic forms. Crystallography basics

49. Polymorphism and allotropic forms. Crystallography basics

50. Polymorphism and allotropic forms. Crystallography basics Isomorphism: Compound having same shape

51. 3 nd Chapter Metal A ny of a class of substances characterized by high electrical and thermal conductivity as well as by malleability,  ductility , and high reflectivity of light. Approximately three-quarters of all known chemical elements are metals. The most abundant varieties in the Earth’s crust are  aluminum ,  iron ,  calcium ,  sodium ,  potassium , and  magnesium . The vast majority of metals are found in ores (mineral-bearing substances), but a few such as  copper ,  gold ,  platinum , and  silver  frequently occur in the free state because they do not readily react with other elements. Metals are malleable , meaning they can be formed into useful shapes or foils. They are ductile , meaning they can be pulled into wires. Metals are good conductors of electricity and heat. How does the bonding in metals help explain these properties? Can the inclusion of metal atoms inside a nanotube provide the same properties? By looking at a model of metallic bonding , we can gain significant insight into these questions. Metals and Ceramics .

52. A  metal is a  material  that, when freshly prepared, polished, or fractured, shows a lustrous appearance, and conducts  electricity  and  heat  relatively well. Metals are typically  malleable  (they can be hammered into thin sheets) or  ductile  (can be drawn into wires). A metal may be a  chemical element  such as  iron ; an  alloy  such as  stainless steel ; or a molecular compound such as  polymeric sulfur nitride . In physics, a metal is generally regarded as any substance capable of conducting electricity at a temperature of  absolute zero . [1]  Many elements and compounds that are not normally classified as metals become metallic under high pressures. For example, the nonmetal  iodine  gradually becomes a metal at a pressure of between 40 and 170 thousand times  atmospheric pressure . Equally, some materials regarded as metals can become nonmetals.  Sodium , for example, becomes a nonmetal at pressure of just under two million times atmospheric pressure. In chemistry, two elements that would otherwise qualify (in physics) as brittle metals— arsenic  and  antimony —are commonly instead recognised as  metalloids  due to their chemistry (predominantly non-metallic for arsenic, and balanced between metallicity and nonmetallicity for antimony). Around 95 of the 118 elements in the  periodic table  are metals (or are likely to be such). The number is inexact as the boundaries between metals,  nonmetals , and  metalloids  fluctuate slightly due to a lack of universally accepted Metals and Ceramics .

53. definitions of the categories involved. In  astrophysics  the term "metal" is cast more widely to refer to all chemical elements in a star that are heavier than  helium , and not just traditional metals. In this sense the first four "metals" collecting in stellar cores through nucleosynthesis are  carbon ,  nitrogen ,  oxygen , and  neon , all of which are strictly non-metals in chemistry. A star  fuses  lighter atoms, mostly hydrogen and helium, into heavier atoms over its lifetime. Used in that sense, the  metallicity  of an astronomical object is the proportion of its matter made up of the heavier chemical elements. [2] [3] Metals, as chemical elements, comprise 25% of the Earth's crust and are present in many aspects of modern life. The strength and resilience of some metals has led to their frequent use in, for example, high-rise building and bridge  construction , as well as most vehicles, many  home appliances , tools, pipes, and railroad tracks.  Precious metals  were historically used as  coinage , but in the modern era,  coinage metals  have extended to at least 23 of the chemical elements. [4 ] Metals and Ceramics .

54. The history of refined metals is thought to begin with the use of copper about 11,000 years ago. Gold, silver, iron (as meteoric iron), lead, and brass were likewise in use before the first known appearance of bronze in the 5th millennium BCE. Subsequent developments include the production of early forms of steel; the discovery of  sodium —the first  light metal —in 1809; the rise of modern  alloy steels ; and, since the end of World War II, the development of more sophisticated alloys. Metals and Ceramics .

55. Metals Properties: Form and structure: Metals are shiny and  lustrous , at least when freshly prepared, polished, or fractured. Sheets of metal thicker than a few micrometres appear opaque, but  gold leaf  transmits green light. The solid or liquid state of metals largely originates in the capacity of the metal atoms involved to readily lose their outer shell electrons. Broadly, the forces holding an individual atom's outer shell electrons in place are weaker than the attractive forces on the same electrons arising from interactions between the atoms in the solid or liquid metal. The electrons involved become delocalised and the atomic structure of a metal can effectively be visualised as a collection of atoms embedded in a cloud of relatively mobile electrons. This type of interaction is called a  metallic bond . [5]  The strength of metallic bonds for different elemental metals reaches a maximum around the center of the  transition metal  series, as these elements have large numbers of delocalized electrons Although most elemental metals have higher  densities  than most  nonmetals , [5]  there is a wide variation in their densities,  lithium  being the least dense (0.534 g/cm3) and  osmium  (22.59 g/cm3) the most dense. Magnesium, aluminum and titanium are  light metals  of significant commercial importance. Their respective densities of 1.7, 2.7 and Metals and Ceramics .

56. Metals Properties: Form and structure: 4.5  g/cm3 can be compared to those of the older structural metals, like iron at 7.9 and copper at 8.9 g/cm3. An iron ball would thus weigh about as much as three aluminum balls of equal volume. High melting point : Most metals have high melting points and all except mercury are solid at room temperature. Sonorous : Metals often make a ringing sound when hit. Reactivity : Some metals will undergo a chemical change (reaction), by themselves or with other elements, and release energy. These metals are never found in a pure form, and are difficult to separate from the minerals. Potassium and sodium are the most reactive metals. They react violently with air and water; potassium will ignite on contact with water! Other metals don’t react at all with other metals. This means they can be found in a pure form (examples are gold and platinum). Because copper is relatively inexpensive and has a low reactivity, it’s useful for making pipes and wiring. Metals and Ceramics .

57. Five groups of metals: Noble Metals  are found as pure metals because they are nonreactive and don’t combine with other elements to form compounds. Because they are so nonreactive, they don’t corrode easily. This makes them ideal for jewelry and coins. Noble metals include copper, palladium, silver, platinum, and gold. Alkali Metals  are very reactive. They have low melting points and are soft enough to be cut with a knife. Potassium and sodium are two alkali metals. Alkaline Earth Metals  are found in compounds with many different minerals. They are less reactive than alkali metals, as well as harder, and have higher melting points. This group includes calcium, magnesium, and barium. Transition Metals  are what we usually think of when we think of metals. They are hard and shiny, strong, and easy to shape. They are used for many industrial purposes. This group includes iron, gold, silver, chromium, nickel, and copper, some of which are also noble metals. Poor Metals  are fairly soft, and most are not used very much by themselves. They become very useful when added to other substances, though. Poor metals include aluminum, gallium, tin, thallium, antimony, and bismuth. Metals and Ceramics .

58. Alloys: Strong Combinations The properties of these different metals can be combined by mixing two or more of them together. The resulting substance is called an  alloy.  Some of our most useful building materials are actually alloys. Steel, for example, is a mixture of iron and small amounts of carbon and other elements; a combination that is both strong and easy to use. (Add chromium and you get stainless steel. Other alloys like brass (copper and zinc) and bronze (copper and tin) are easy to shape and beautiful to look at. Bronze is also used frequently in ship-building because it is resistant to corrosion from sea water. Titanium is much lighter and less dense than steel, but as strong; and although heavier than aluminum, it’s also twice as strong. It’s also very resistant to corrosion. All these factors make it an excellent alloy material. Titanium alloys are used in aircraft, ships, and spacecraft, as well as paints, bicycles, and even laptop computers! Gold, as a pure metal, is so soft that it is always mixed with another metal (usually silver, copper, or zinc) when it’s made into jewelry. The purity of gold is measured in  karats . The purest you can get in jewelry is 24 karats, which is about 99.7% pure gold. Gold can also be mixed with other metals to change its color; white gold, which is popular for jewelry, is an alloy of gold and platinum or palladium. Metals and Ceramics .

59. Metal from Ore Ores are  rocks or minerals  from which a valuable substance – usually metal – can be extracted. Some common ores include galena (lead ore), bornite and malachite (copper), cinnabar (mercury), and bauxite (aluminum). The most common iron ores are magnetite and hematite (a rusty-colored mineral formed by iron and oxygen), which both contain about 70% iron. There are several processes for  refining  iron from ore. The older process is to burn iron ore with charcoal (carbon) and oxygen provided by bellows. The carbon and oxygen, including the oxygen in the ore, combine and leave the iron. However, the iron does not get hot enough to melt completely and it contains silicates left over from the ore. It can be heated and hammered out to form  wrought iron . The more modern process uses a  blast furnace  to heat iron ore, limestone, and coke (a coal product). The resulting reactions separate out the iron from the oxygen in the ore. This ‘pig iron’ needs to be further mixed to create wrought iron. It can also be used for another important purpose: when heated with carbon and other elements, it becomes a stronger metal called  steel . Metals and Ceramics .

60. Corrosion: Process & Prevention When oxygen reacts with a metal, it forms an  oxide  on the surface of the metal. In some metals, like aluminum, this is a good thing. The oxide provides a protective layer that keeps the metal from corroding further . Iron and steel, on the other hand, have serious problems if they are not treated to prevent corrosion. The reddish oxide layer that forms on iron or steel when it reacts with oxygen is called  rust . The rust layer continually flakes away, exposing more of the metal to corrosion until the metal is eventually eaten through One common way to protect iron is to coat it with special paint that keeps oxygen from reacting with the metal underneath the paint. Another method is  galvanization : in this process, steel is coated with zinc. The oxygen, water molecules, and carbon dioxide in the air react with the zinc, forming a layer of zinc carbonate that protects from corrosion. Look around your house, yard, and garage for examples of corrosion as well as galvanization and other means of protecting metal from rust. Metals and Ceramics .

61. Ceramics . A  ceramic  is any of the various hard, brittle, heat-resistant and  corrosion-resistant  materials made by shaping and then firing an inorganic, nonmetallic material, such as  clay , at a high temperature.  Common examples are  earthenware ,  porcelain , and  brick . The earliest ceramics made by humans were  pottery  objects ( pots  or  vessels ) or  figurines  made from  clay , either by itself or mixed with other materials like  silica , hardened and  sintered  in fire. Later, ceramics were  glazed  and fired to create smooth, colored surfaces, decreasing  porosity  through the use of glassy, amorphous ceramic coatings on top of the crystalline ceramic surface. Ceramics now include domestic, industrial and building products, as well as a wide ranic materials were developed for use in advanced ceramic engineering, such as in  semiconductors . The word  " ceramic "  comes from the  Greek   word  ( keramikos ),  "of pottery"  or  "for pottery " ,  from  κέραμος  ( keramos ),  "potter's clay, tile, pottery" .  Metals and Ceramics .

62. Ceramics . Ceramic material is an inorganic, non-metallic oxide, nitride, or carbide material. Some elements, such as  carbon  or  silicon , may be considered ceramics. Ceramic materials are brittle, hard, strong in compression, and weak in  shearing  and tension. They withstand chemical erosion that occurs in other materials subjected to acidic or caustic environments. Ceramics generally can withstand very high temperatures, ranging from 1,000 °C to 1,600 °C (1,800 °F to 3,000 °F). The  crystallinity  of ceramic materials varies widely. Most often, fired ceramics are either  vitrified (glass) or semi-vitrified as is the case with earthenware,  stoneware , and porcelain. Varying crystallinity and  electron  composition in the ionic and covalent bonds cause most ceramic materials to be good thermal and  electrical insulators  (researched in  ceramic engineering ). With such a large range of possible options for the composition/structure of a ceramic (nearly all of the elements, nearly all types of bonding, and all levels of crystallinity ), the breadth of the subject is vast, and identifiable attributes ( hardness ,  toughness ,  electrical conductivity ) are difficult to specify for the group as a whole. General properties such as high melting temperature, high hardness, poor conductivity, high  moduli of elasticity , chemical resistance and low ductility are the norm, with known exceptions to each of these rules Metals and Ceramics .

63. Ceramics . ( piezoelectric ceramics ,  glass transition  temperature,  superconductive ceramics ). composites , such as  fiberglass  and  carbon fiber , while containing ceramic materials are not considered to be part of the ceramic family . Highly oriented crystalline ceramic materials are not amenable to a great range of processing. Methods for dealing with them tend to fall into one of two categories – either make the ceramic in the desired shape, by reaction  in situ , or by "forming" powders into the desired shape, and then form into a solid body.  Ceramic forming techniques  include shaping by hand (sometimes including a rotation process called "throwing"),  slip casting ,  tape casting  (used for making very thin ceramic capacitors),  injection molding , dry pressing, and other variations. Many ceramics experts do not consider materials with  amorphous  ( noncrystalline ) character (i.e., glass) to be ceramics even though glassmaking involves several steps of the ceramic process and its mechanical properties are similar to ceramic materials. However, heat treatments can convert glass into a semi-crystalline material known as  glass-ceramic Traditional ceramic raw materials include clay minerals such as  kaolinite , whereas more recent materials include aluminum oxide, more commonly known as  alumina . The modern Metals and Ceramics .

64. Ceramics . ceramic materials, which are classified as advanced ceramics, include  silicon carbide  and  tungsten carbide . Both are valued for their abrasion resistance and hence find use in applications such as the wear plates of crushing equipment in mining operations. Advanced ceramics are also used in the medicine, electrical, electronics industries, and body armor . Properties The physical properties of any ceramic substance are a direct result of its crystalline structure and chemical composition.  Solid-state chemistry  reveals the fundamental connection between microstructure and properties, such as localized density variations, grain size distribution, type of porosity, and second-phase content, which can all be correlated with ceramic properties such as mechanical strength,   hardness ,  toughness ,  dielectric constant , and the  optical  properties exhibited by  transparent materials . Ceramography  is the art and science of preparation, examination, and evaluation of ceramic microstructures. Evaluation and characterization of ceramic microstructures are often implemented on similar spatial scales to that used commonly in the emerging field of nanotechnology: from tens of  ångstroms  (Å) to tens of micrometers (µm). This is typically Metals and Ceramics .

65. Ceramics . carbide  and  tungsten carbide . somewhere between the minimum wavelength of visible light and the resolution limit of the naked eye . The microstructure includes most grains, secondary phases, grain boundaries, pores, micro-cracks, structural defects, and hardness micro indentions. Most bulk mechanical, optical, thermal, electrical, and magnetic properties are significantly affected by the observed microstructure. The fabrication method and process conditions are generally indicated by the microstructure. The root cause of many ceramic failures is evident in the cleaved and polished microstructure. Physical properties which constitute the field of  materials science  and  engineering  include the following : Mechanical properties Mechanical properties are important in structural and building materials as well as textile fabrics. In modern  materials science , fracture mechanics is an important tool in improving the mechanical performance of materials and components. It applies the  physics  of  stress  and  strain , in particular the theories of  elasticity  and  plasticity , to the microscopic  crystallographic defects  found in real materials in order to predict the macroscopic mechanical failure of bodies.  Fractography  is widely used with fracture Metals and Ceramics .

66. Ceramics . mechanics to understand the causes of failures and also verify the theoretical  failure  predictions with real-life failures . Ceramic materials are usually  ionic  or  covalent  bonded materials. A material held together by either type of bond will tend to  fracture  before any  plastic deformation  takes place, which results in poor  toughness  in these materials. Additionally, because these materials tend to be porous, the  pores  and other microscopic imperfections act as  stress concentrators , decreasing the toughness further, and reducing the  tensile strength . These combine to give  catastrophic failures , as opposed to the more ductile  failure modes  of metals. These materials do show  plastic deformation . However, because of the rigid structure of crystalline material, there are very few available slip systems for  dislocations  to move, and so they deform very slowly. To overcome the brittle behavior, ceramic material development has introduced the class of  ceramic matrix composite  materials, in which ceramic fibers are embedded and with specific coatings are forming fiber bridges across any crack. This mechanism substantially increases the fracture toughness of such ceramics. Ceramic  disc brakes  are an example of using a ceramic matrix composite material manufactured with a specific process Metals and Ceramics .

67. Ceramics . Ice- templating for enhanced mechanical properties If ceramic is subjected to substantial mechanical loading, it can undergo a process called  ice- templating , which allows some control of the  microstructure  of the ceramic product and therefore some control of the mechanical properties. Ceramic engineers use this technique to tune the mechanical properties to their desired application. Specifically,  strength  is increased, when this technique is employed. Ice templating allows the creation of macroscopic pores in a unidirectional arrangement. The applications of this oxide strengthening technique are important for  solid oxide fuel cells  and  water filtration  devices . To process a sample through ice templating , an aqueous  colloidal suspension  is prepared to contain the dissolved ceramic powder evenly dispersed throughout the colloid ,  for example  Yttria -stabilized zirconia  (YSZ). The solution is then cooled from the bottom to the top on a platform that allows for unidirectional cooling. This forces  ice  crystals to grow in compliance with the unidirectional cooling and these ice crystals force the dissolved YSZ particles to the solidification front of the solid-liquid interphase boundary, resulting in pure ice crystals lined up unidirectionally alongside concentrated pockets of colloidal particles. The sample is then simultaneously heated and the pressure is reduced enough to force the Metals and Ceramics .

68. Ceramics . ice crystals to  sublimate (change the form)  and the YSZ pockets begin to  anneal  together to form macroscopically aligned ceramic microstructures. The sample is then further  sintered  to complete the  evaporation  of the residual water and the final consolidation of the ceramic microstructure . During ice- templating , a few variables can be controlled to influence the pore size and morphology of the microstructure. These important variables are the initial solids loading of the colloid, the cooling rate, the sintering temperature and duration, and the use of certain additives which can influence the microstructural morphology during the process. A good understanding of these parameters is essential to understanding the relationships between processing, microstructure, and mechanical properties of unequal porous materials Metals and Ceramics .

69. Ceramics . Electrical properties Semiconductors Some ceramics are  semiconductors . Most of these are  transition metal oxides  that are II-VI semiconductors, such as  zinc oxide . While there are prospects of mass-producing blue  LEDs ( ight -emitting diode) from zinc oxide, ceramicists are most interested in the electrical properties that show  grain boundary  effects. One of the most widely used of these is the varistor ( semiconductor diode with resistance dependent ). These are devices that exhibit the property that resistance drops sharply at a certain  threshold voltage . Once the voltage across the device reaches the threshold, there is a  breakdown  of the electrical structure in the vicinity of the grain boundaries, which results in its  electrical resistance  dropping from several megohms down to a few hundred  ohms . The major advantage of these is that they can dissipate a lot of energy, and they self-reset; after the voltage across the device drops below the threshold, its resistance returns to being high. This makes them ideal for  surge-protection  applications; as there is control over the threshold voltage and energy tolerance, they find use in all sorts of applications. The best demonstration of their ability can be found in  electrical substations , where they are employed to protect the infrastructure from  lightning  strikes. They have rapid response Metals and Ceramics .

70. Ceramics . low maintenance, and do not appreciably degrade from use, making them virtually ideal devices for this application. Semiconducting ceramics are also employed as  gas sensors . When various gases are passed over a polycrystalline ceramic, its electrical resistance changes. With tuning to the possible gas mixtures, very inexpensive devices can be produced. Superconductivity Under some conditions, such as extremely low temperature, some ceramics exhibit  high-temperature superconductivity . The reason for this is not understood, but there are two major families of superconducting ceramics Ferroelectricity (reversal of flow) and supersets Piezoelectricity , a link between electrical and mechanical response, is exhibited by a large number of ceramic materials, including the quartz used to  measure time  in watches and other electronics. Such devices use both properties of piezoelectrics , using electricity to produce a mechanical motion (powering the device) and then using this mechanical motion to produce electricity (generating a signal). The unit of time measured is the natural interval required for electricity to be converted into mechanical energy and back again. Metals and Ceramics .

71. Ceramics . The piezoelectric effect is generally stronger in materials that also exhibit  pyroelectricity (generate a temporary voltage), and all pyroelectric materials are also piezoelectric. These materials can be used to inter-convert between thermal, mechanical, or electrical energy; for instance, after synthesis in a furnace, a pyroelectric crystal allowed to cool under no applied stress generally builds up a static charge of thousands of volts. Such materials are used in  motion sensors , where the tiny rise in temperature from a warm body entering the room is enough to produce a measurable voltage in the crystal. In turn, pyroelectricity is seen most strongly in materials that also display the  ferroelectric effect , in which a stable electric dipole can be oriented or reversed by applying an electrostatic field. Pyroelectricity is also a necessary consequence of ferroelectricity . This can be used to store information in  ferroelectric capacitors , elements of  ferroelectric RAM . The most common such materials are  lead zirconate titanate  and  barium titanate . Aside from the uses mentioned above, their strong piezoelectric response is exploited in the design of high-frequency  loudspeakers , transducers for  sonar . Metals and Ceramics .

72. Ceramics . Positive thermal coefficient Temperature increases can cause grain boundaries to suddenly become insulating in some semiconducting ceramic materials, mostly mixtures of  heavy metal   titanates . The critical transition temperature can be adjusted over a wide range by variations in chemistry. In such materials, current will pass through the material until  joule heating  brings it to the transition temperature, at which point the circuit will be broken and current flow will cease. Such ceramics are used as self-controlled heating elements in, for example, the rear-window defrost circuits of automobiles. At the transition temperature, the material's  dielectric  response becomes theoretically infinite. While a lack of temperature control would rule out any practical use of the material near its critical temperature, the dielectric effect remains exceptionally strong even at much higher temperatures . Metals and Ceramics .

73. Ceramics . Optical properties Optically transparent materials  focus on the response of a material to incoming light waves of a range of wavelengths.  Frequency selective optical filters  can be utilized to alter or enhance the brightness and contrast of a digital image. Guided lightwave transmission via frequency selective  waveguides  involves the emerging field of fiber  optics  and the ability of certain glassy compositions as a  transmission medium  for a range of frequencies simultaneously ( multi-mode optical fiber ) with little or no  interference  between competing  wavelengths  or frequencies. This  resonant   mode  of  energy  and  data transmission  via electromagnetic (light)  wave propagation , though low powered, is virtually lossless. Optical waveguides are used as components in  Integrated optical circuits  (e.g.  light-emitting diodes , LEDs) or as the transmission medium in local and long haul  optical communication  systems. Also of value to the emerging materials scientist is the sensitivity of materials to radiation in the thermal  infrared  (IR) portion of the  electromagnetic spectrum . This heat-seeking ability is responsible for such diverse optical phenomena as  Night-vision  and IR  luminescence . Thus, there is an increasing need in the  military  sector for high-strength, robust materials Metals and Ceramics .

74. Ceramics . Optical properties 1. Barium titanate :  (often mixed with  strontium titanate ) displays  ferroelectricity , meaning that its mechanical, electrical, and thermal responses are c 2. Sialon  ( Silicon Aluminium Oxynitride )  has high strength; resistance to thermal shock, chemical and wear resistance, and low density. These ceramics are used in non-ferrous molten metal handling, weld pins, and the chemical industry . 3. Silicon carbide  ( SiC )  is used as a  susceptor  in microwave furnaces, a commonly used abrasive, and as a  refractory  material . 4. Silicon nitride  (Si 3 N 4 )  is used as an  abrasive  powder . 5. Steatite (magnesium silicates)  is used as an  electrical insulator . 6. Titanium carbide  Used in space shuttle re-entry shields and scratchproof watches . 7. Uranium oxide  ( U O 2 ) , used as  fuel  in  nuclear reactors . 8. Yttrium barium copper oxide  (Y Ba 2 Cu 3 O 7−x ) , another high temperature  superconductor . Metals and Ceramics .

75. Ceramics . Optical properties 9. Zinc oxide  ( Zn O ) , which is a  semiconductor , and used in the construction of  varistors . 10. Zirconium dioxide  (zirconia) , which in pure form undergoes many  phase changes  between room temperature and practical  sintering  temperatures, can be chemically "stabilized" in several different forms. Its high oxygen  ion conductivity  recommends it for use in  fuel cells  and automotive  oxygen sensors . In another variant,  metastable  structures can impart  transformation toughening  for mechanical applications; most  ceramic knife  blades are made of this material. Partially stabilised zirconia (PSZ) is much less brittle than other ceramics and is used for metal forming tools, valves and liners, abrasive slurries, kitchen knives and bearings subject to severe abrasion. Metals and Ceramics .

76. Ceramics . usage C eramic products are usually divided into four main types; these are shown below with some examples : 1.Structural , including  bricks ,  pipes ,  floor  and  roof tiles 2. Refractories , such as  kiln  linings, gas fire radiants ,  steel  and glass making crucibles 3. Whitewares , including  tableware , cookware, wall tiles, pottery products and sanitary ware  4.Technical , also known as engineering, advanced, special, and fine ceramics. Such items include : gas burner  nozzles , ballistic protection ,  vehicle armor , nuclear fuel  uranium oxide pellets, biomedical implants ,coatings of  jet engine   turbine   blades , Ceramic matrix composite  gas turbine parts , Reinforced carbon–carbon  ceramic  disc brakes , missile  nose cones , bearing (mechanical) tiles used in the  Space Shuttle program Metals and Ceramics .

77. Ceramics . Applications : 1.Knife blades:  blade of a  ceramic knife  will stay sharp for much longer than that of a steel knife, although it is more brittle and susceptible to breaking . 2. Carbon-ceramic brake disks:  for vehicles are resistant to  brake fade  at high temperatures . 3. " Advanced  composite ceramic and metal matrices"  have been designed for most modern  armoured fighting vehicles  because they offer superior penetrating resistance against  shaped charges  ( HEAT  rounds) and  kinetic energy penetrators . 4 . " Ceramics such as  alumina  and  boron carbide "  have been used in  ballistic armored vests  to repel high-velocity  rifle  fire. Such plates are known commonly as  small arms protective inserts , or SAPIs. Similar material is used to protect the  cockpits  of some military airplanes, because of the low weight of the material . 5 .Ceramics can be used in place of steel for  ball bearings . Their higher hardness means they are much less susceptible to wear and typically last for triple the lifetime of a steel part. They also deform less under load, meaning they have less contact with the bearing retainer walls and can roll faster. In very high-speed applications, heat from  friction  during rolling can cause Metals and Ceramics .

78. Ceramics . Applications : problems for metal bearings, which are reduced by the use of ceramics. Ceramics are also more chemically resistant and can be used in wet environments where steel bearings would rust. In some cases, their electricity-insulating properties may also be valuable in bearings. Two drawbacks to ceramic bearings are a significantly higher cost and susceptibility to damage under shock loads . 6 .In the early 1980s,  Toyota  researched production of an  adiabatic   engine  using ceramic components in the hot gas area. The ceramics would have allowed temperatures of over 1650°C. The expected advantages would have been lighter materials and a smaller cooling system (or no need for one at all), leading to a major weight reduction. The expected increase of  fuel efficiency  of the engine (caused by the higher temperature, as shown by  Carnot's  theorem) could not be verified experimentally; it was found that the heat transfer on the hot ceramic cylinder walls was higher than the transfer to a cooler metal wall as the cooler gas film on the metal surface works as a  thermal insulator . Thus, despite all of these desirable properties, such engines have not succeeded in production because of costs for the ceramic components and the limited advantages. (Small imperfections in the ceramic Metals and Ceramics .

79. Ceramics . Applications : material with its low  fracture toughness  lead to cracks, which can lead to potentially dangerous equipment failure.) Such engines are possible in laboratory settings, but mass production is not feasible with current technology . 7.Work is being done in developing ceramic parts for  gas turbine   engines . Currently, even blades made of  advanced metal alloys  used in the engines' hot section require cooling and careful limiting of operating temperatures. Turbine engines made with ceramics could operate more efficiently, giving aircraft greater range and payload for a set amount of fuel. 8.Recent advances have been made in ceramics which include  bioceramics , such as dental implants and synthetic bones.  Hydroxyapatite , the natural mineral component of bone, has been made synthetically from several biological and chemical sources and can be formed into ceramic materials. Orthopedic implants coated with these materials bond readily to bone and other tissues in the body without rejection or inflammatory reactions so are of great interest for gene delivery and  tissue engineering  scaffolds. Most hydroxyapatite ceramics are very porous and lack mechanical strength, and are used to coat metal orthopedic devices to aid in forming a bond to bone or as bone fillers. They are also used as fillers for orthopedic Metals and Ceramics .

80. Ceramics . plastic screws to aid in reducing inflammation and increase the absorption of these plastic materials. Work is being done to make strong, fully dense nanocrystalline hydroxyapatite ceramic materials for orthopedic weight bearing devices, replacing foreign metal and plastic orthopedic materials with a synthetic, but naturally occurring bone mineral. Ultimately, these ceramic materials may be used as bone replacements or with the incorporation of protein  collagens , synthetic bones. 8.Durable actinide-containing ceramic materials have many applications such as in nuclear fuels for burning excess Pu and in chemically-inert sources of alpha irradiation for power supply of unmanned space vehicles or to produce electricity for microelectronic devices. Both use and disposal of radioactive actinides require their immobilization in a durable host material. Nuclear waste long-lived radionuclides such as actinides are immobilized using chemically-durable crystalline materials based on polycrystalline ceramics and large single crystals . 10.High-tech ceramic is used in watchmaking for producing watch cases. The material is valued by watchmakers for its lightweight, scratch resistance, durability, and smooth touch.  IWC  is one of the brands that initiated the use of ceramic in watchmaking. [19] Metals and Ceramics .

81. 4 Th Chapter Energy and Chemistry Energy Energy is the capacity of a physical system to do work. The common symbol for energy is the uppercase letter  E . The standard unit is the  joule , symbolized by J. One joule (1 J) is the energy resulting from the equivalent of one  newton  (1 N) of force acting over one meter (1 m) of  displacement . There are two main forms of energy, called  potential energy  and  kinetic energy . Potential energy, sometimes symbolized  U , is energy stored in a system. A stationary object in a gravitational field, or a stationary charged particle in an electric field, has potential energy. Kinetic energy is observable as motion of an object, particle, or set of particles. Examples include the falling of an object in a gravitational field, the motion of a charged particle in an electric field, and the rapid motion of  atom s or molecules when an object is at a temperature above zero  Kelvin . Thermo-chemistry

82. 4 Th Chapter Energy Matter is equivalent to energy in the sense that the two are related by the Einstein equation: E  =  mc 2 where  E  is the energy in joules,  m  is the mass in kilograms, and  c  is the  speed of light , equal to approximately 2.99792 x 10 8  meters per second. In electrical circuits, energy is a measure of  power  expended over time. In this sense, one joule (1 J) is equivalent to one  watt  (1 W) dissipated or radiated for one  second  (1 s). A common unit of energy in electric utilities is the kilowatt-hour (kWh), which is the equivalent of one kilowatt (kW) dissipated or expended for one hour (1 h). Because 1 kW = 1000 W and 1 h = 3600 s, 1 kWh = 3.6 x 10 6  J. Heat energy is occasionally specified in British thermal units ( Btu ) by nonscientists, where 1 Btu is approximately equal to 1055 J. The heating or cooling capability of a climate-control system may be quoted in Btu, but this is technically a misuse of the term. In this sense, the system manufacturer or vendor is actually referring to Btu per hour (Btu/h), a measure of heating or cooling power. Thermo-chemistry

83. 4 Th Chapter Thermo-chemistry Thermochemistry  is the study of the heat energy which is associated with  chemical reactions  and/or physical transformations. A reaction may release or absorb energy, and a phase change may do the same, such as in  melting  and  boiling . Thermochemistry focuses on these energy changes, particularly on the  system 's energy exchange with its  surroundings . Thermochemistry is useful in predicting reactant and product quantities throughout the course of a given reaction. In combination with  entropy  determinations, it is also used to predict whether a reaction is spontaneous (immediate) (produced product under given condition) or non-spontaneous, favorable or unfavorable. Endothermic reactions  absorb heat, while  exothermic reactions  release heat. Thermochemistry combine into one the concepts of thermodynamics with the concept of energy in the form of chemical bonds. The subject commonly includes calculations of such quantities as  heat capacity ,  heat of combustion ,  heat of formation ,  enthalpy ,  entropy ,  free energy , and  calories . Thermo-chemistry

84. 4 Th Chapter Heat and Work Heat is the flow of energy between two objects, from the warmer one to the cooler one , because of a difference in their temperatures. Thus if we are speaking carefully , heat is a process and not a quantity . Although we routinely hear statements such as “ turn up the heat,” heat is not an entity we can pump into a room or a cup of coffee . An object does not possess heat. In a strictly scientific sense, a furnace does not produce heat but rather a body of warm air or hot water that has a higher temperature than the cool air in a room. What emerges from the vent on the floor is not “heat ,” but warm air. Although these distinctions are essentially meaningful, they can be very important in many cases . Work is the transfer of energy accomplished by a force moving a mass some distance against resistance. Lifting a set of roller coaster cars up a hill against the pull of gravity is an example of work. When we consider macroscopic examples, we are typically viewing work in terms of mechanical energy . Work, however, encompasses a wider range of phenomena than just mechanical movement of macroscopic objects. The most common type of work we will Thermo-chemistry

85. 4 Th Chapter Heat and Work encounter in chemical processes is pressure-volume work (PV-work) . When a gas expands, it can do work. If an inflated balloon is released before it is tied off, it flies around as the gas inside the balloon expands into the large volume of the room . Because the flying balloon has mass, it is easy to see that the expanding gas is doing work on the balloon: this is pressure-volume work . For a more productive example of work being done by a chemical reaction, we might look at the burning of gasoline in a car engine. Gasoline is actually a complex mixture of hydrocarbons. The energy needed to propel a car is released by the combustion of those hydrocarbons in the engine cylinders . Hydrocarbon + O2(g) : CO2(g) + H2O(g) This combustion produces carbon dioxide and water vapor, and those gases do PV-work as they expand against the piston in the cylinder. This PV-work is then transmitted through the drive train to move the car. Thermo-chemistry

86. 4 Th Chapter Energy Transformation and Conservation of Energy The multiple forms of energy are not all equally useful, so in many cases it is desirable to transform energy from one form into another. For example, the lighting in room is provided by electricity , but that electricity was probably generated by the release of chemical energy through the combustion of coal. Chemical energy released as the coal burns and then convert it to electrical energy. That electrical energy must then be conveyed to room , where light bulbs convert it into radiant energy . The first and foremost constraint on energy transformation is that total energy must be conserved . It need to define a number of terms. The system is defined as the part of the universe that is being considered. The remainder of the universe is referred to as the surroundings , even though it is not generally necessary to consider everything else in the actual universe. These definitions assure that the system plus the surroundings must equal the universe . The system and the surroundings are separated by a boundary . In some cases, this boundary may be a physical container, and in others, it might be a more abstract separation . Thermo-chemistry

87. 4 Th Chapter Energy Transformation and Conservation of Energy Once an appropriate choice of a system has been made, the concept of conservation of energy immediately becomes useful. Because we said that heat and work are the only possible forms of energy transfer, we can attribute the overall change in energy , E , of a system to these two components. Heat is commonly designated as q and work as w, so we can write ∆ E = q + w (Change in internal Energy) The symbol ∆ (delta) is introduced here as a notation meaning “the change in.” is always defined as the difference between the final state and the initial state. ∆ E = E final – E initial Convention dictates that energy transferred into a system is given a positive sign and energy flowing out of a system carries a negative sign . Thus when heat flows into a system from the surroundings, the value of q is positive , and when work is done on a system, the value of w is positive. Conversely , when heat flows out of a system or work is done by the system on the surroundings , q and w will be negative Thermo-chemistry

88. 4 Th Chapter Energy Transformation and Conservation of Energy EXAMPLE If 515 J of heat is added to a gas that does 218 J of work as a result, what is the change in the energy of the system? Solution Heat added TO the system means that q > 0, so q = +515 J. Work done BY the system means that w < 0, so w = –218 J. ∆ E = q + w = 515 J + (–218 J) = +297 J Now ∆ E = q + w (Change in internal Energy ) State that “ Energy can be transformed from one form to another but cannot be created or destroyed. This is known as the first law of thermodynamics .” Which is called the Law of conservation of Energy. Thermo-chemistry

89. 4 Th Chapter Waste Energy The combustion of gasoline is not inherently useful, but when the heat released is harnessed in the engine of an automobile, the resulting work gets us where we need to go. All available observations, however, point to the idea that it is impossible to convert heat completely to work. The car’s engine gets hot when it runs. The heat that warms the engine does not propel the car toward its destination . So a portion of the energy released by the combustion of gasoline does not contribute to the desired work of moving the car. In terms of the energy economy , this energy can be considered wasted. One common way to obtain work from a system is to heat it: heat flows into the system and the system does work. But in practice, the amount of heat flow will always exceed the amount of useful work achieved. The excess heat may contribute to thermal pollution . ( Thermal pollution is the raising or lowering of water temperature in streams , lakes, or oceans above or below normal seasonal ranges from the discharge of hot or cold waste streams into the water.) The efficiency of conversion from heat to work can be expressed as a percentage . Thermo-chemistry

90. 4 Th Chapter Waste Energy Table Typical efficiencies of some common energy conversion devices Device Energy Conversion Typical Efficiency (%) Electric heater Electrical : thermal 100 Hair drier Electrical : thermal 100 Electric generator Mechanical : electrical 95 Electric motor (large ) Electrical : mechanical 90 Battery Chemical : electrical 90 Steam boiler (power plant) Chemical : thermal 85 Home gas furnace Chemical : thermal 85 Home oil furnace Chemical : thermal 65 Electric motor (small ) Electrical : mechanical 65 Home coal furnace Chemical : thermal 55 Steam turbine Thermal : mechanical 45 Gas turbine (aircraft) Chemical : mechanical 35 Gas turbine (industrial) Chemical : mechanical 30 Automobile engine Chemical : mechanical 25 Thermo-chemistry

91. 4 Th Chapter Heat Capacity and Calorimetry Heat Capacity D ifferent systems will absorb different amounts of energy (heat) based on three main factors: the amount of material, the type of material, and the temperature change. The general expression for Heat capacity is given as: q = mc ∆ T Where q is the heat capacity, m is mass of the material c is the specific heat of material and ∆ T is the difference or change in temperature. The specific heat is a physical property of a material that measures how much heat is required to raise the temperature of one gram of that material by 1°C. Similarly, the molar heat capacity is a physical property that describes how much heat is required to raise the temperature of one mole of a substance by 1°C. So if we choose to express the amount of material in terms of moles rather than mass, our equation changes only slightly. q = nc p ∆ T OR q = nc v ∆ T Thermo-chemistry

92. 4 Th Chapter Calorimetry Calorimetry is the term used to describe the measurement of heat flow ( heat flow into or out of a system). Experiments are carried out in devices called calorimeters. It is the process of measuring the amount of heat released or absorbed during a chemical reaction. The heat evolved or absorbed by the system of interest is determined by measuring the temperature change in its surroundings. Every effort is made to isolate the calorimeter thermally, preventing heat flow between the immediate surroundings and the rest of the universe. If the instrument is thermally isolated from the rest of the universe, the only heat flow that must be considered is that between the system being studied and the immediate surroundings , whose temperature can be measured . A two-step process is used to make a calorimetric measurement. The first step is calibration in which a known amount of heat is generated in the apparatus. The second step is the actual measurement, in which we determine the amount of heat absorbed or released in the reaction of a known amount of material. The calibration can be done either by burning a known amount of a well-characterized material or by resistive heating, in which a known amount of current is passed through a wire that heats due to its electrical resistance. Thermo-chemistry

93. 4 Th Chapter Calorimetry The heat capacity of the entire calorimeter may be obtained by measuring the change in temperature of the surroundings resulting from a known heat input. Known amount of heat = calorimeter constant × ∆ T , Or q = C calorimeter × ∆ T

94. 4 Th Chapter Heat Capacity and Calorimetry Calorimetry Note that in contrast to our earlier equations relating q and ∆ T , there is no mass or number of moles term here for the quantity of material. The calorimeter constant is the heat capacity of a particular object (or set of objects) rather than that of a material . It may help to think of it as the heat capacity “per calorimeter” and then realize that we have just one calorimeter. For someone who routinely uses the same calorimeter , this approach is much simpler than the alternative, which would be to keep track of the masses of steel, water, and other materials in the calorimeter. In the case of a bomb calorimeter, the calorimeter constant is largely attributable to the water that surrounds the bomb but also includes the heat capacities of the thermometer, the stirring system, and the bomb itself . Thermo-chemistry

95. 4 Th Chapter EXAMPLE A calorimeter is to be used to compare the energy content of some fuels. In the calibration of the calorimeter, an electrical resistance heater supplies 100.0 J of heat and a temperature increase of 0.850°C is observed. Then 0.245 g of a particular fuel is burned in this same calorimeter, and the temperature increases by 5.23°C. Calculate the energy density of this fuel, which is the amount of energy liberated per gram of fuel burned. Strategy :The calibration step allows us to determine the calorimeter constant . Once this is known, the amount of heat evolved from the fuel can be determined by using Equation. Finally, we divide this heat by the mass of fuel that generated it to arrive at the requested energy density. Solution Step 1: Calibration q = C calorimeter × ∆ T So C calorimeter = q / ∆ T = 100.0 J/0.850°C C calorimeter = 118 J/° C Thermo-chemistry

96. 4 Th Chapter EXAMPLE Step 2: Determination of heat evolved by fuel q calorimeter = C calorimeter × ∆ T = 118 J/°C × 5.23°C = 615 J And q fuel = – q calorimeter = –615 J Step 3: Calculation of the energy density Energy density = – q fuel /m = –(–615 J)/0.245 g = 2510 J/g = 2.51 kJ/g Discussion This problem illustrates the need to be careful with signs in thermodynamic calculations . Because the burning of fuel releases heat, q for the fuel should be negative . The energy density, though, would be reported as a positive number, resulting in the additional negative sign in the final step. Thermo-chemistry

97. 4 Th Chapter Enthalpy The  enthalpy   of a thermodynamic system is defined as the sum of its internal energy and the product of its pressure and volume (work done) By using the definition of internal energy , the change in internal energy ∆ E equals the sum of heat flow and work. ∆ E = q + w In chemical reactions, we usually need to consider only PV-work. When a gas expands, it does an amount of work equal to P ∆ V on its surroundings. But if the expanding gas is our system, we want w to be the work done on the gas, and that will be – P ∆ V . So we can replace w in the equation above with – P ∆ V . ∆ E = q – P ∆ V If the volume is held constant, ∆ V is zero, so the second term is zero. All that remains is ∆ E = q v where subscript “v ” denote that the equation is correct under constant volume conditions. Thermo-chemistry

98. 4 Th Chapter Enthalpy If the experiment is at constant pressure, than above equation will became H = E + PV Where “H” is known as enthalpy which is the sum of its internal energy and the product of its pressure and volume (work) Working from this definition , we can show that the change in enthalpy (∆ H ) will be equal to the heat flow under constant pressure conditions. From the above definition, the change in enthalpy (∆ H ) must be ∆ H = ∆ E + ∆ ( PV ) We can expand this by substituting for ∆E using ∆ H = ( q – P ∆ V ) + ∆ ( PV ) If the pressure is held constant, then the ∆ ( PV ) term will simply become P ∆ V , giving ∆ H = q – P ∆ V + P ∆ V The second and third terms clearly cancel and leave the desired result. ∆ H = q p Thermo-chemistry

99. 4 Th Chapter Enthalpy The enthalpy change therefore equals the heat flow under constant pressure. (This is denoted with a subscript “ p”.) Now we have two ways to define heat flow into a system, under two different sets of conditions. For a process at constant volume, the measurable heat flow is equal to ∆ E , the change in internal energy. For a process at constant pressure, the measurable heat flow is equal to the change in enthalpy, ∆ H . A reaction carried out in a beaker in the chemistry laboratory, for instance, occurs under constant pressure conditions (or very nearly so). Thus, when we refer to the heat of a process , we are typically referring to a change in enthalpy, ∆ H . As in previous definitions , ∆ H refers to H final – H initial . When heat evolves from a system, the process is said to be exothermic and the value of ∆ H is less than zero. An exothermic process feels hot: if you pick up the beaker in which an exothermic reaction is taking place, heat will flow from the reacting system into your hand. Conversely, when heat is absorbed by the system, the process is said to be endothermic , and the value of ∆ H is greater than zero. Endothermic processes feel cold because they draw heat from their surroundings. Thermo-chemistry

100. 4 Th Chapter Enthalpy ∆ H of Phase Changes Heat flow into a substance does not always raise its temperature. If heat flows into an ice cube at 0°C, for example, the ice will melt to form liquid water at 0°C. (If heat continues to flow into the resulting water, its temperature will begin to rise, of course .) How can the temperature remain constant despite the influx of heat? To understand this , we need to remember that intermolecular forces are more extensive in a solid than in a liquid. So as the ice cube melts, energy must be expended to overcome some of the intermolecular attractions. The internal energy of liquid water is higher than that of solid ice, even though both are at the same temperature. For similar reasons, there will be heat flow in any phase change. The names of phase changes among solids, liquids, and gases are summarized in Figure. Because these phase changes generally take place at constant pressure, the corresponding heat flows should be viewed as changes in enthalpy. Some phase changes are so common that their enthalpy changes have Thermo-chemistry

101. 4 Th Chapter Enthalpy ∆ H of Phase Changes specific names and symbols assigned to them. The heat required to melt a substance is the heat of fusion , ∆ H fus . The enthalpy change for converting a liquid to a gas is known as the heat of vaporization , ∆ H vap . We know that when a liquid is converted to a gas, all the molecules in a sample must overcome whatever intermolecular forces are present. That means that energy must flow into the substance to vaporize it, so the heat of vaporization will always be positive. It follows that the reverse process, condensation, will always release heat. The values of enthalpy changes in opposite directions have the same numeric value and differ only in their signs. Because the strength of the intermolecular forces varies from one substance to another, the magnitude of the enthalpy change for any phase transition will also depend on the substance involved . Thermo-chemistry

102. 4 Th Chapter Enthalpy ∆ H of Phase Changes Thermo-chemistry

103. 4 Th Chapter Enthalpy ∆ H of Phase Changes In the case of Phase change, the amount of ice undergoing the transition : it will take more heat to melt a large block of ice than a small cube. Then the amount of water in terms of moles, leading to the following equation : ∆ H = n × ∆ H phase change Here n is the number of moles, as usual. Notice that this relationship does not include ∆ T . This should make sense if we keep in mind that phase changes occur at a constant temperature, so there is no ∆ T in the transition . Thermo-chemistry

104. 4 Th Chapter Enthalpy ∆ H of Phase Changes EXAMPLE Calculate the enthalpy change when 240. g of ice melts. Strategy The ∆ H fus value in Table 9.3 is in J/ mol , so the amount of ice must be converted into moles. Multiplying the number of moles by ∆ H fus will provide the desired quantity . Solution 240 g H2O × 1 mol /18.0 g = 13.3 mol H2O ∆ H = n × ∆ H fus = 13.3 mol × 6009.5 J/ mol = 8.01 × 104 J Thermo-chemistry

105. 4 Th Chapter Enthalpy Vaporization and Electricity Production The large amount of energy needed for converting water from a liquid to a gas, as by the series of processes shown in Figure, is exploited in converting chemical energy into electricity. The basic features of a fossil fuel–powered electricity plant are shown. When the fuel—typically coal or natural gas—burns, chemical energy is released as heat. The goal of the power plant is to convert as much of this energy as possible into electricity. The critical step in this process is to trap the heat given off in the combustion reaction. Water is the material of choice for this process because it has a large heat of vaporization. R ecall that intermolecular forces are unusually strong in water because of extensive hydrogen bonding. These hydrogen bonds between water molecules in the liquid lead to the large value of ∆ H vap . If a material with a small heat of vaporization were substituted for water, much more of it would be required to absorb the same amount of heat. The large heat of vaporization coupled with the relative abundance of water has led to its widespread use in the energy sector of the economy. Thermo-chemistry

106. 4 Th Chapter Enthalpy Vaporization and Electricity Production Thermo-chemistry

107. 4 Th Chapter

108. 4 Th Chapter Enthalpy Heat of Reaction So far we have considered enthalpy changes for simple physical processes such as temperature changes and phase transitions. But the importance of chemistry to the energy economy arises from the fact that there are enthalpy changes in chemical reactions as well . This enthalpy change is commonly referred to as the heat of reaction . Because many reactions are carried out under constant pressure conditions. Bonds and Energy Chemical reactions involve energy changes because chemical bonds are broken and formed when reactants are transformed into products. Consider a fairly simple reaction—the combustion of methane . CH4(g ) + 2 O2(g) : CO2(g) + 2 H2O(ℓ ) Lewis structure is: Thermo-chemistry

109. 4 Th Chapter Enthalpy Bonds and Energy On the reactant side of the equation, we have four C-H single bonds and two O=O double bonds. On the product side, we have two C=O double bonds and four O-H single bonds. Over the course of the reaction, all bonds in the reactants must be broken, and that will require an input of energy. On the other hand, all bonds in the products must be formed, and that will release energy. (Recall that bond formation is always exothermic and bond breaking is always endothermic.) If the energy released in forming new bonds is greater than the energy required to break the original bonds , then the overall reaction should be exothermic. Conversely, if the energy needed for bond breaking is greater than that released in bond making, then the reaction will be endothermic . Because methane is the principal component of natural gas, we know that burning it must release energy. So we should anticipate that this particular reaction must be exothermic, and calorimetric measurements bear this out; ∆ H for the combustion of one mole of methane is –890.4 kJ. Thermo-chemistry

110. 4 Th Chapter Enthalpy Bonds and Energy For the combustion of methane, the thermochemical equation is CH4(g) + 2 O2(g) : CO2(g) + 2 H2O(ℓ) ∆ H = –890.4 kJ This equation tells us two important things. First, we can immediately see whether the reaction is exothermic or endothermic because ∆ H carries a sign. We know that the combustion of methane must be exothermic, and the negative sign on ∆ H confirms this . Second, the thermochemical equation includes the numerical value of ∆ H , so we can tell exactly how much heat will be released. It is important to realize that the heat of reaction shown is for the equation exactly as written; if one mole of methane reacts with two moles of oxygen, 890.4 kJ will be released. But if more fuel is burned , more heat will be released. So if the stoichiometric coefficients are multiplied by some factor , the heat of reaction must also be multiplied by that factor. Thus another thermochemical equation for the combustion of methane is 2 CH4(g) + 4 O2(g) : 2 CO2(g) + 4 H2O(ℓ ) ∆ H = –1780.8 kJ Thermo-chemistry

111. 4 Th Chapter Enthalpy Heats of Reaction for Some Specific Reactions Some classes of chemical reactions have been assigned their own label for heats of reaction. The example reaction for methane falls into one such category, combustion. Because combustion is a common part of the energy economy, enthalpy changes for combustion reactions are used to compare various fuels. Sometimes these heats of combustion are designated as ∆ H comb . Similarly, the neutralization reactions between acids and bases have heats of reaction that are called heats of neutralization, ∆ H neut . Another class of reactions, formation reactions designated heats of reaction known as heats of formation , ∆ H f ° . A formation reaction is the chemical reaction by which one mole of a compound is formed from its elements in their standard states . The standard state is the most stable form of the element at room temperature (25°C ) and pressure (1 atm ). The formation reaction for carbon monoxide is C(s ) + ½ O2(g ) : CO(g ) ∆ H ° = ∆ H f °[ CO(g )] Thermo-chemistry

112. 4 Th Chapter Enthalpy Heats of Reaction for Some Specific Reactions Note that the definition of the formation reaction immediately implies that the heat of formation for any element in its standard state must always be zero. To see this , imagine writing the formation reaction for an element in its standard state, such as O2(g ). We would need one mole of O2(g) as the product and oxygen in its standard state as the reactant. But because the standard state of oxygen is O2(g), our formation reaction is really no reaction at all. O2(g ) : O2(g) ∆ H = ∆ H f °[ O2(g )] = Because both sides of this equation are the same, there can be no change in enthalpy . So ∆ H ° must be zero . This will be true for any element in its standard state . Thermo-chemistry

113. 4 Th Chapter Enthalpy Heats of Reaction for Some Specific Reactions Because we require just one mole of CO on the right-hand side, we must use a fractional coefficient on the O2 to balance the equation, even though this may look odd . Two very common errors when writing formation reactions are including elements that are not in their standard states or having more than one mole of product compound . For carbon monoxide, these mistakes might produce either of the following incorrect “formation” reactions. C(s) + O(g) : CO(g ) ∆ H ° ≠ ∆ H f°[ CO(g)] 2 C(s) + O2(g) : 2 CO(g ) ∆ H ° ≠ ∆ H f°[ CO(g)] Although both are valid chemical equations, they do not describe the formation reaction for CO. The first reaction is not correct because oxygen is not shown in its standard state, as a diatomic molecule. The second reaction is not correct because two moles of carbon monoxide are formed. Formation reactions are quite useful for determining heats of reaction. Thermo-chemistry

114. 4 Th Chapter Hess’s Law and Heats of Reaction Hess’s Law To obtain information about heats of reaction indirectly, Hess’s law is use i.e., the enthalpy change for any process is independent of the particular way the process is carried out. The underlying concept upon which this idea is built is that enthalpy is a state function . A state function is a variable whose value depends only on the state of the system and not on its history. When you drive your car, your location is a state function, but the distance that you have traveled to get there is not . For a chemical reaction, the concept of state functions can be very important . We rarely if ever know the microscopic details of how reactant molecules are actually converted into product molecules. But it is relatively easy to determine what the reactants and the products are. Because enthalpy is a state function, if we can find a way to determine the change in enthalpy for any particular path that leads from the reactants to the desired products, we will know that the result will apply for whatever actual path the reaction may take. The block diagram in Figure illustrates this concept . Thermo-chemistry

115. 4 Th Chapter Hess’s Law For the situation shown in Figure, the desired enthalpy change could be obtained via either of two alternative pathways. ∆ H desired = ∆ H A i + ∆ H A f ∆ H desired = ∆ H B i + ∆ H B f Thermo-chemistry

116. 4 Th Chapter Hess’s Law Hess’s law has important practical implications. Many times we can break a chemical reaction down into a series of steps whose net result is the same as that of the original reaction. According to Hess’s law, in such a case, we can evaluate the enthalpy of the original reaction by using the sequential ones . Thermo-chemistry

117. 4 Th Chapter Hess’s Law EXAMPLE Sulfur trioxide reacts with water to form sulfuric acid, a major contributor to acid rain . One origin of SO 3 is the combustion of sulfur, which is present in small quantities in coal , according to the following equation . S(s) + 3/2 O 2 (g ) SO 3 (g) Given the thermochemical information below, determine the heat of reaction for this reaction . S(s ) + O2(g ) SO2(g) ∆ H ° = –296.8 kJ 2 SO 2 (g) + O 2 (g ) 2 SO 3 (g ) ∆ H ° = –197.0 kJ Thermo-chemistry

118. 4 Th Chapter Hess’s Law Solution: We start with the first of the two given reactions. S(s ) + O2(g ) SO2(g) ∆ H ° = –296.8 kJ Next multiply the second given reaction by one-half. This will account for the fact that the desired reaction produces only one mole of SO3. 1/2 x [2 SO 2 (g) + O 2 (g ) 2 SO 3 (g ) ∆ H ° = –197.0 kJ] This gives an equation in which one mole of SO2 is consumed, along with its enthalpy change . SO 2 (g ) +1/2 O 2 (g ) SO 3 (g ) ∆ H ° = –98.0 kJ] Adding this to the first reaction above gives the desired amount of SO3 and the heat of reaction: Thermo-chemistry

119. 4 Th Chapter Hess’s Law Solution: S(s) + O2(g) SO2(g) ∆ H ° = –296.8 kJ SO 2 (g ) +1/2 O 2 (g ) SO 3 (g ) ∆ H ° = –98.5 kJ] S(s) +3/2 O 2 (g) SO 3 (g ) ∆ H ° = – 3 95.3 kJ Both of the reactions we added are exothermic, so it makes sense that the combination would be more exothermic than either of the individual reactions . Thermo-chemistry

120. 4 Th Chapter Formation Reactions and Hess’s Law Thermo-chemistry

121. 4 Th Chapter Formation Reactions and Hess’s Law Step 1 is the decomposition of reactants into elements in their standard states . But this is just the opposite of the formation reaction of the reactants, so the enthalpy change of the process is – ∆ H f° ( reactants). Similarly, Step 2, the formation of the products from elements in their standard states, has an enthalpy change of ∆ H f ° ( products ). Remember, however, that the formation reaction is defined for the generation of one mole of the compound. Consequently, to use tabulated heats of formation we must multiply by the stoichiometric coefficients ( Nos of elements) from the balanced equation to account for the number of moles of reactants consumed or products generated . Taking these factors into account leads to one of the more useful equations in thermochemistry. In this equation we have designated the stoichiometric coefficients by the Greek letter ν. The first summation is over all of the reactants, and the second is over all of the products. Two example problems will show how heats of formation are used in understanding the thermochemistry of reactions useful in producing energy . Thermo-chemistry

122. 4 Th Chapter EXAMPLE Use tabulated data to find the heat of combustion of one mole of propane, C3H8, to form gaseous carbon dioxide and liquid water. Strategy We will need values for the heats of formation of the reactants and products to determine the desired heat of combustion. First, we must write a balanced chemical equation for the process. Then we can use Equation to calculate the heat of the reaction (in this case the heat of combustion) by looking up heats of formation in the table in Appendix E. The stoichiometric coefficients needed will be obtained from the balanced equation. Remember that the heat of formation of an element in its standard state—like the O2 in this equation—will always be zero. Solution Thermo-chemistry

123. 4 Th Chapter Thermo-chemistry

124. 4 Th Chapter EXAMPLE Ethanol, C2H5OH, is used to introduce oxygen into some blends of gasoline. It has a heat of combustion of 1366.8 kJ/mol. What is the heat of formation of ethanol ? Strategy We know the relationship between the heat of combustion of a reaction and the heats of formation of the substances involved. We will need a balanced chemical equation for the combustion, and we must recognize that the combustion of ethanol yields the same products as hydrocarbon combustion. We can write the balanced equation and then use Equation to determine the desired quantity. In this case, we know the heat of reaction and will be solving for one of the heats of formation. Thermo-chemistry

125. 4 Th Chapter Thermo-chemistry

126. 5 Th Chapter Electrochemistry Electrochemistry is the branch of  physical chemistry  concerned with the relationship between electrical potential, as a measurable and quantitative phenomenon, and identifiable  chemical change , with either electrical potential as an outcome of a particular chemical change, or vice versa. These reactions involve electrons moving between electrodes via an electronically-conducting phase (typically, but not necessarily, an external electrical circuit such as in  electrolessplating ), separated by an ionically -conducting and electronically insulating electrolyte (or ionic  species  in a  solution ). When a chemical reaction is effected by a potential difference, as in  electrolysis , or if electrical potential results from a chemical reaction as in a  battery  or fuel cell, it is called an  electrochemical  reaction. Unlike chemical reactions, in electrochemical reactions electrons (and necessarily resulting ions), are not transferred directly between molecules, but via the aforementioned electronically- and ionically -conducting circuits, respectively. This phenomenon is what distinguishes an electrochemical reaction from a chemical reaction. Electrochemistry

127. 5 Th Chapter Electrolysis Electrolysis , process by which  electric current  is passed through a substance to effect a chemical change. The chemical change is one in which the substance loses or gains an  electron  ( oxidation i.e., losing electron or reduction i.e., gaining electron). The process is carried out in an  electrolytic cell , an apparatus consisting of positive and negative  electrodes  held apart and dipped into a solution containing positively and negatively charged ions. The substance to be transformed may form the  electrode , may  constitute  the solution, or may be dissolved in the solution. Electric current (i.e.,  electrons ) enters through the negatively charged electrode ( cathode ); components of the solution travel to this electrode, combine with the electrons, and are transformed (reduced). The products can be neutral elements or new molecules. Components of the solution also travel to the other electrode ( anode ), give up their electrons, and are transformed (oxidized) to neutral elements or new molecules. If the substance to be transformed is the electrode, the reaction is often one in which the electrode dissolves by giving up electrons . Electrochemistry

128. 5 Th Chapter Electrolysis Electrolytic cells can be divided into two categories based on the nature of the electrodes used . If the electrodes are chemically inert materials that simply provide a path for electrons, the process is called passive electrolysis. When the electrodes are part of the electrolytic reaction, we have active electrolysis. Passive electrolysis is used in industry to purify metals that corrode easily. Active electrolysis is used to plate materials to provide resistance to corrosion. Electrolysis is used extensively in metallurgical processes, such as in extraction ( electrowinning ) or purification ( electrorefining ) of metals from ores or  compounds  and in  deposition  of metals from solution (electroplating). Metallic  sodium  and  chlorine  gas are produced by the electrolysis of molten sodium chloride; electrolysis of an aqueous solution of  sodium chloride  yields sodium hydroxide and chlorine gas. Hydrogen and  oxygen  are produced by the electrolysis of  water Electrochemistry

129. 5 Th Chapter Electrolysis Electrolysis  is the passage of electricity through an electrolyte, with cations moving to the cathode to get reduced, and anions moving towards the anode to get oxidized. An  electrolyte  is a liquid that conducts electricity. Let's first go through a few quantitative measures involved in electrolysis. Let's take a look at the relationship between current, charge, and time. How is a current produced? An  electric current  arises whenever there is a flow of charges (for example, electrons) and is defined as the rate at which charge flows. The formula is as follows: Current = Quantity of charge/Time, or I = Q/t, where I is the current in  Ampere  (A), which is the flow of 1 Coulomb of charge per second, or C/s, t is time in seconds, and Q is quantity of electricity in Coulombs Electrochemistry

130. 5 Th Chapter Faraday's Constant Do you know how much charge is carried by a single electron? The answer is 1.6023 x 10  -19  C. What will then be the total charge carried by one mole of electrons? 1 mole of electrons is represented by the Avogadro's Number, L = 6.022 x 10 23  electrons. Therefore, 6.022 x 10 23  electrons carries a charge of 6.022 x 10 23  x 1.6023 x 10 -19  C/ mol = 96,485 C/mol. 96,485 C/ mol , or one Faraday, denoted by the symbol F, is the amount of electricity that is carried by one mole of electrons and is known as the  Faraday constant . Equivalent weight or equivalent mass is another quantity which is often used in electrolytic calculations and is given by: Equivalent weight , or E = Atomic weight/ Valency , where atomic weight or atomic mass is in g/ mol and the value is usually provided.  Valency  is an atom's ability to combine with other atoms, and equivalent weight or equivalent mass is measured in grams. Electrochemistry

131. 5 Th Chapter Laws of electrolysis The Laws of electrolysis state that (1) the amount of chemical change produced by current at an electrode-electrolyte boundary  is proportional to the quantity of electricity used  and (2) the amounts of chemical changes produced by the same quantity of electricity in different substances are proportional to their equivalent weights . These are called Faraday's laws of electrolysis. What is the first law of electrolysis ? Faraday's First Law of Electrolysis Faraday's First Law of Electrolysis states that “The mass of a substance deposited at any electrode is directly proportional to the amount of charge passed .” or “ the quantity of reaction taking place in terms of mass of ions formed or discharged from an electrolyte is proportional to the amount of electric current passed .” Electrochemistry

132. 5 Th Chapter Laws of electrolysis The mass of the substance (m) deposited or liberated at any electrode is directly proportional to the quantity of electricity or charge (Q) passed. In the mathematical form, this law can be represented as follows : m α Removing the proportionality sign gives m = ZQ, where m is the mass in grams (g), Q is measured in Coulombs (C), and Z is the proportionality constant in g/C (in grams per coulomb) and is also known as the  electrochemical equivalent , which is the mass of a substance produced at the electrode during electrolysis by one Coulomb of charge. Faraday further observed that 1 Faraday (96,485C) of charge liberates 1 gram equivalent of the substance at the electrodes. This means that 1C will liberate one gram equivalent of a substance/96,485, which is the electrochemical equivalent (Z) of the substance.   Electrochemistry

133. 5 Th Chapter Laws of electrolysis This goes to a relationship between electrochemical equivalent (Z) and equivalent weight or equivalent mass (E) of a substance, and this can be expressed as: Z = Equivalent weight/96,485, or Z = E/96,485 Moving back to the equation m = ZQ, it can alternately be written as: m = Z x I x t ( since Q/t = I or Q = I x t) m = E x I x t /96,485 (since Z = E/96,485) Let's now wrap up all what we've learned so far in two examples: 1. During an electrolysis of molten sodium chloride, a 4A current is passed through electrodes for 1 hour. Calculate the mass of sodium that is produced during this time. Given I = 4A, t = 1 x 60 x 60 = 3,600s, and E of sodium is 23/1 = 23g Mass of sodium produced = E x I x t/96,485 = (23 x 4 x 3,600)/96,485 = 3.43g Electrochemistry

134. 5 Th Chapter Questions Calculate the amount of copper metal (in moles) that can be generated with 300 C of electricity. 2 . What is the time needed to deposit 25 g of silver from a solution of silver nitrate at 2 A? Solutions 1. Moles of Copper Generated We have : Q = 300 C F = 96,500 C/ mol First, write the reduction reaction of copper. Cu^{+2} + 2e^- → Cu Calculate the moles of electrons. n = Q / F = 300 / 96500 = 0.0031 mol Next, determine the moles of copper from the balanced chemical equation. Electrochemistry

135. 5 Th Chapter Questions 1 mol electrons = 0.5 mol Cu 0.0031 moles / 2 = 0.00155 mol Cu 0.00155 moles of copper are generated. 2. Time to Deposit 25 g of Silver We have: mass Ag = 25 g I = 2 A F = 96,500 C/ mol molar mass of silver = 107.9 g/ mol First, calculate the moles of silver. moles Ag = 25 / 107.9 = 0.232 mol Write the reduction reaction for silver: Electrochemistry

136. 5 Th Chapter Ag ^+ + e^- → Ag (s) There is a 1:1 ratio between electrons and silver deposited. moles of electrons = 0.232 mol Calculate the electricity needed. Q = n × F Q = 0.232 × 96,500 = 22,388 C Finally, calculate the time. Q = I × t 22,388 = 2 × t t = 11,194 seconds 11,194 / 60 = 186.56 min 186.56 / 60 = 3.1 hrs The time needed is 3.1 hours. Electrochemistry

137. 5 Th Chapter Ag ^+ + e^- → Ag (s) There is a 1:1 ratio between electrons and silver deposited. moles of electrons = 0.232 mol Calculate the electricity needed. Q = n × F Q = 0.232 × 96,500 = 22,388 C Finally, calculate the time. Q = I × t 22,388 = 2 × t t = 11,194 seconds 11,194 / 60 = 186.56 min 186.56 / 60 = 3.1 hrs The time needed is 3.1 hours. Electrochemistry

138. 5 Th Chapter Faraday’s Second Law of Electrolysis So far we have learned that the mass of the chemical, deposited due to electrolysis is proportional to the quantity of electricity that passes through the electrolyte. The mass of the chemical, deposited due to electrolysis is not only proportional to the quantity of electricity passes through the electrolyte, but it also depends upon some other factor. Every substance will have its own atomic weight. So for the same number of atoms, different substances will have different masses. Again, how many atoms deposited on the electrodes also depends upon their number of valency . If valency is more, then for the same amount of electricity, the number of deposited atoms will be less whereas if valency is less, then for the same quantity of electricity, more number of atoms to be deposited. So, for the same quantity of electricity or charge passes through different electrolytes, the mass of deposited chemical is directly proportional to its atomic weight and inversely proportional to its valency . Faraday’s second law of electrolysis states that, when the same quantity of electricity is Electrochemistry

139. 5 Th Chapter Faraday’s Second Law of Electrolysis passed through several electrolytes, the mass of the substances deposited are proportional to their respective chemical equivalent or equivalent weight. Chemical Equivalent or Equivalent Weight The chemical equivalent or equivalent weight of a substance can be determined by Faraday’s laws of electrolysis , and it is defined as the weight of that subtenance which will combine with or displace the unit weight of hydrogen. The chemical equivalent of hydrogen is, thus, unity. Since valency of a substance is equal to the number of hydrogen atoms, which it can replace or with which it can combine, the chemical equivalent of a substance, therefore may be defined as the ratio of its atomic weight to its valency . chemical equivalent = atomic weight/ valency Electrochemistry

140. INDUSTRIAL CHEMISTRY Industrial chemistry as the branch of chemistry which applies physical and chemical procedures towards the transformation of natural raw materials and their derivatives to products that are of benefit to humanity . The scope of industrial chemistry therefore includes: The exploitation of materials and energy in appropriate scale Application of science and technology to enable humanity experience the benefits of chemistry in areas such as food production , health and hygiene, shelter, protection, decoration, recreation and entertainment. 6 Th Chapter

141. CLASSIFICATION OF INDUSTRIES Industry is a general term that refers to all economic activities that deal with production of goods and services. Manufacturing Building and construction Agriculture Trade Energy Finance Transport Communication Education Tourism

142. THE MANUFACTURING INDUSTRY Manufacturing industry is a compartment of industry or economy which is concerned with the production or making of goods out of raw materials by means of a system of organized labor. Food, beverages and tobacco Textiles, wearing apparel, leather goods Paper products, printing and publishing Chemical, petroleum, rubber and plastic products Non-metallic mineral products other than petroleum products Basic metal products, machines and equipment.

143. THE CHEMICAL INDUSTRY The chemical industry can also be classified according to the type of main raw materials used and/or type of principal products made. We therefore have industrial inorganic chemical industries and industrial organic chemical industries. Industrial inorganic chemical Industries extract inorganic chemical substances, make composites of the same and also synthesize inorganic chemicals. Heavy industrial organic chemical industries produce petroleum fuels, polymers, petrochemicals and other synthetic materials, mostly from petroleum. Light organic industries produce specialty chemicals which include pharmaceuticals, dyes, pigments and paints, pesticides, soaps and detergents, cosmetic products and miscellaneous products.

144. COMMODITY CHEMICALS The global chemical industry is founded on basic inorganic chemicals (BIC) and basic organic chemicals (BOC) and their intermediates. Because they are produced directly from natural resources or immediate derivatives of natural resources, they are produced in large quantities. In the top ten BIC , almost all the time, sulphuric acid, nitrogen, oxygen, ammonia, lime, sodium hydroxide, phosphoric acid and chlorine dominate. The reason sulphuric acid is always number one is because it is used in the manufacture of fertilizers, polymers, drugs, paints, detergents and paper. It is also used in petroleum refining, metallurgy and in many other processes. The top ranking of oxygen is to do with its use in the steel industry . Ethylene and propylene are usually among the top ten BOC. They are used in the production of many organic chemicals including polymers. BIC and BOC are referred to as commodity or industrial chemicals. Commodity chemicals are therefore defined as low-valued products produced in large quantities mostly in continuous processes. They are of technical or general purpose grade.

145. SPECIALTY CHEMICALS High-value adding involves the production of small quantities of chemical products for specific end uses. Such products are called specialty chemicals. These are high value-added products produced in low volumes and sold on the basis of a specific function. In this category are the so-called performance chemicals which are high value products produced in low volumes and used in extremely low quantities. They are judged by performance and efficiency. Enzymes and dyes are performance chemicals. Other examples of specialty chemicals include medicinal chemicals, agrochemicals, pigments, flavour and fragrances, personal care products, surfactants and adhesives. Specialty chemicals are mainly used in the form of formulations. Purity is of vital importance in their formulation. This calls for organic synthesis of highly valued pure chemicals known as fine chemicals

146. FINE CHEMICALS At times you will find that the raw materials for your product need to be very pure for the product to function as desired. Research chemicals are in this category as also are pharmaceutical ingredients. Such purified or refined chemicals are called fine chemicals. By definition they are high value-added pure organic chemical substances produced in relatively low volumes and sold on the basis of exact specifications of purity rather than functional characteristics.

147. RAW MATERIAL FOR THE CHEMICAL INDUSTRY All chemicals are derived from raw materials available in nature. The price of chemicals depends on the availability of their raw materials. Major chemical industries have therefore developed around the most plentiful raw materials The natural environment is the source of raw materials for the chemical industry . The atmosphere is the field above ground level. It is the source of air from which six industrial gases namely N 2 , O 2 , Ne, Ar , Kr and Xe are manufactured. The mass of the earth’s atmosphere is approximately 5 x 10 15 tons and therefore the supply of the gases is virtually unlimited. Ocean water which amounts to about 1.5 x 10 21 litres contains about 3.5 percent by mass dissolved material. Seawater is a good source of sodium chloride, magnesium and bromine. The vast majority of elements are obtained from the earth’s crust in the form of mineral ores, carbon and hydrocarbons. Coal, natural gas and crude petroleum besides being energy sources are also converted to thousands of chemicals . Vegetation and animals contribute raw materials to the so-called agro-based industries. Oils, fats, waxes, resins, sugar, natural fibres and leather are examples of thousands of natural products.

148. THE CHEMICAL PROCESSES Every industrial process is designed to produce a desired product from a variety of starting raw materials using energy through a succession of treatment steps integrated in a rational fashion. The treatments steps are either physical or chemical in nature . Energy is an input to or output in chemical processes. The layout of a chemical process indicates areas where: raw materials are pre-treated conversion takes place separation of products from by-products is carried out refining/purification of products takes place entry and exit points of services such as cooling water and steam

149. UNITS THAT MAKE UP A CHEMICAL PROCESS A chemical process consists of a combination of chemical reactions such as synthesis (combining different items), calcination (heating), ion exchange, electrolysis, oxidation, hydration and operations based on physical phenomena such as evaporation, crystallization, distillation and extraction A chemical process is therefore any single processing unit or a combination of processing units used for the conversion of raw materials through any combination of chemical and physical treatment changes into finished products. There are many types of chemical processes that make up the global chemical industry. However, each may be broken down into a series of steps called unit operations. These are the physical treatment steps, which are required to: put the raw materials in a form in which they can be reacted chemically put the product in a form which is suitable for the market

150. PROCESS FLOW DIAGRAMS To simplify process description, flow diagrams also known as flow sheets are used . A flow diagram is a road map of the process, which gives a great deal of information in a small space. Chemical engineers use it to show the sequence of equipment and unit operations in the overall process to simplify the visualization of the manufacturing procedures and to indicate the quantities of material and energy transferred. A flow diagram is not a scale drawing but it: pictorially identifies the chemical process steps in their proper/logical sequence includes sufficient details in order that a proper mechanical interpretation may be made Two types of flow diagrams are in common use, namely, the block diagrams and the process flow diagrams.

151. BLOCK DIAGRAMS This is a schematic diagram, which shows: what is to be done rather than how it is to be done. Details of unit operations/processes are not given flow by means of lines and arrows unit operations and processes by figures such as rectangles and circles raw materials, intermediate and final products

152. A block diagram for a sulphuric acid plant

153. PROCESS FLOW DIAGRAM / FLOW SHEET Flow sheet symbols are pictorial quick-to-draw, easy-to-understand symbols that transcend language barriers. Some have already been accepted as national standards while others are symbols commonly used in chemical process industries, which have been proven to be effective. Engineers are constantly devising their own symbols where standards do not exist. Therefore, symbols and presentation may vary from one designer or company to another.

154. MATERIAL BALANCES Mass balance calculations serve the following purposes: They help us know the amount and composition of each stream in the process. The calculations obtained in 1 form the basis for energy balances through the application of the l aw of conservation of energy. We are able to make technical and economic evaluation of the process and process units from the knowledge of material and energy consumption and product yield obtained. We can quantitatively know the environmental emissions of the process. In mass balance calculations, we begin with two assumptions There is no transfer of mass to energy Mass is conserved for each element or compound on either molar or weight basis It is important to note the following: Mass and atoms are conserved Moles are conserved only when there is no reaction Volume is not conserved. You may write balances on total mass, total moles, mass of a compound, moles of an atomic species, moles of a compound, mass of a species, etc.

155. MATERIAL BALANCE EQUATIONS We might be tempted to think that in a process, INPUT =OUTPUT In practice, some material may accumulate in the process or in some particular process units. For example, in a batch process, some material may remain adhered to the walls of containers. In the dehydration of ethane to ethylene, possible chemical reactions are as follows: C 2 H 6 (g) C 2 H 4(g) C 2 H 6 (g) 2C (s) +3H 2(g) C 2 H 4(g) 2C (s) +2H 2(g) The carbon formed accumulates in the reactor.

156. Because processes may be batch with no inflow and outflow or continuous with inflow and outflow, and that there may be conversion of chemical species, a good mass balance equation takes care of all these aspects. The following is a general mass balance equation. Accumulation within the system = Flow In through the system boundaries - Flow Out through the system boundaries + generation within the system - Consumption within the system

157. Simply put: Accumulation =Flow in – Flow out + Production – Consumption The system is any process or portion of a process chosen for analysis. A system is said to be "open" if material flows across the system boundary during the interval of time being studied; "closed" if there are no flows in or out. Accumulation is usually the rate of change of holdup of material within the system. If material is increasing, accumulation is positive; if it is decreasing, it is negative. If the system does not change with time, it is said to be at steady state , and the net accumulation will be zero.

158. MASS BALANCE CALCULATION PROCEDURE The general procedure for carrying out mass balance calculations is as follows: Make a block diagram (flow sheet) over the process Put numbers on all the streams List down all the components that participate in the process. Find the components that are in each stream and list them adjacent to the stream in the block diagram Decide on an appropriate basis for the calculations e.g. 100kg raw material A, 100kg/ hr A, 1 ton of product, 100 moles reactant B etc. Find out the total number of independent relations. This is equivalent to the total number of stream components. Put up different relations between stream components and independent relations to calculate concentrations Tabulate results.