SOLUCIONES QUIMICAS. UNIDADES FISICAS Y QUIMICAS

SOLUCIONES

1. SOLUTIONS
Chapter 13

2. What is a solution?
In chemistry, a solutionis a homogenous mixture
composed of two or more substances. In such a
mixture, a soluteis dissolved in another
substance, known as a solvent. A common
example is a solid, such as salt or sugar,
dissolved in water,aliquid.
A mixtureis a substance made by combining two
or more different materials in such a way that no
chemical reaction occurs. The objects do not bond
together in a mixture. A mixture can usually be
separated back into its original components.
Some examples of Mixtures are oil, ocean water
and soil.

3. A suspensionis a heterogenous fluid
containing solid particles that are sufficiently
large for sedimentation.
A colloidis a homogeneous solution with
intermediate particle size between a solution
and a suspension.

5. What is concentration?
Solvent: The substance in which the solute
dissolves to make the solution.
Solute: The substance dissolved in a solution.
Aqueous: Describes a solution in which the
solvent is water.
Concentration: The quantity of solute in a
specific quantity of solvent or solution.
Molarity: A concentration unit, expressed in
moles of solute per liter of solution.

6. Molarity(M) = moles of solute/liters of
solution=mol/L

7. Class Practice
What is the molarity of a potassium chloride
solution that has a volume of 400 ml and
contains 85 g of KCl?
Sodium thiosulfate, Na
2S
2O
3,is used as a fixer
when developing photographic film. What is
the mass in grams of Na
2S
2O
3 needed to
make 100ml of a 0.250M solution?

8. Home work
Page 475 Practice problems do all odd #.

9. Separating mixtures
There are many ways to separate mixtures
into their components.
distillation
Magnetic
separation
filtering
chromatography

10. Different ways of separating
mixture
1 A magnetcan be used to separate IRON from SAND.
How it works: The magnet sticks to the iron but not to the sand.
3. Filtering (filtration) can be used to separate a solid (or
suspension) from a liquid.
How it works: The liquid (and anything dissolved in the liquid)
passes through holes in the filter paper but the solid particles are
too big and get stuck.
Example: Filtrationwould be used to separate the dirt from some
salty water.
4. Evaporationcan be used to separate a dissolved SOLUTE from
a SOLUTION
Example: Evaporationwould be used to obtain some pure saltfrom
salty water.
How it works: When salty water is warmed the water evaporates
leaving behind crystals of salt.

11. Distillationis a method of separating chemical
substances based on differences in their
volatilities in a boiling liquid mixture. Example:
Used to separate crude oil into more fractions for
specific uses such as transport, power generation
and heating.
Chromatography is a physical method of
separation in which the components to be
separated are distributed between two phases,
one which is the stationary (stationary phase)
while the other (the mobile phase) moves in a
definite direction..

12. Gas Solubility
Gases can dissolve in liquids: Gases may
dissolve in liquids, for example, carbon dioxide or
oxygen in water.
Gas solubility depends on pressure: A soda
bottle can be considered to be saturatedsince
there is some soda above the liquid level and
some is in the liquid itself.In an unopened soda
bottle there is much higher partial pressure of CO
2
in the neck of the bottle, above the liquid than there is
in the air outside the bottle. Due to this difference in
the pressure the CO
2dissolves in the liquid.

13. Gas solubility decreases with increasing
temperature: After the soda bottle is opened
the soda is allowed to warm, the soda forms
fewer bubbles and tastes flat.

14. Liquids and miscibilities
Miscible: Indicates liquids that will dissolve in
each other.
Immiscible: Indicates liquids that will not
dissolve appreciably in each other example oil
and water.

15. Polarity of the solute and
solvent
Polar solvents dissolve polar compounds, and
non polar solvents dissolve non polar
compounds example when a sugar cube
having polar sucrose molecules is dissolved in
water a polar solvent.

16. Hydrogen bonding : High solubility is expected
when hydrogen bonds form between solute
and solvent molecules.
Two compounds that are both polar or both
non polar are likely to be miscible.
Two compounds that can form hydrogen
bonds with each other are likely to be miscible.

17. Solubility principles at work
Dry cleaners use solubility principles to
remove stains. Commonly used dry cleaning
solvent is tetrachloro ethylene C
2Cl
4.
Vitamin C dissolves in water. Some sources of
vitamin C are,

18. Vitamin A dissolves in oils and fats. Vitamin A
affects vision because the human body uses it
to make a pigment called visual purple, one of
the vital light sensitive molecule in the retina.

19. Conductivity in Solutions
Conductivity is a measure of water’s ability to
conduct electrical current. Measurements of
conductivity provide a general indication of
water quality.

20. Electrical conductivityis a measure of a
material's ability to conduct an electric current.
When an electrical potential difference is
placed across a conductor, its movable
charges flow, giving rise to an electric current.
The conductivity σ is defined as the ratio of the
current density to the electric field strength :

21. Electrolytes
What are electrolytes?
Electrolytes are substances that become ions
in solution and acquire the capacity to conduct
electricity.
Non electrolyte is a substance that does not
dissociate into ions and so in solution it is a
nonconductor of electricity.

22. Non electrolyte in solution
Weak electrolyte

23. Strong electrolyte

24. Tap water conducts electricity:
You should avoid water when you are using
electricity. Unlike distilled water that does not
conduct enough electricity to light a bulb in the
conductivity apparatus tap water contains
various ions from dissolved minerals. Water
sources like water from a well has more
concentration of salts than the surface water
such as lakes and rivers.

25. While swimming in the pool, get out of the
pool if a thunderstorm strikes. Chlorinated
water conducts electricity.

26. Dissociation: A process in which a compound
separates into fragments, such as simpler
molecules,atoms,radicals or ions.
Hydration: The process by which water
molecules surround each ion as it moves into
solution.

27. Factors affecting solubility
Temperature:The solubility of a given solute in a
given solvent often depends on temperature. For
around 95% of solid solutes, the solubility
increases with temperature, but gaseous solutes
exhibit more complex behavior. As the
temperature is raised gases usually become less
soluble in water, but more soluble in organic
solvents.

28. Pressure:Henry’s Law states that the solubility of a gas
is directly proportional to the pressure of that gas, which
may be written as p=kc
where k is a constant.
Polarity: "Like dissolves like" This indicates that a solute
will dissolve best in a solvent that has a similar polarity
to itself. For example, a very polar (hydrophilic) solute
such as urea is highly soluble in highly polar water, less
soluble in fairly polar methanol, and practically insoluble
in non-polar solvents such as benzene.

29. Colligative properties
Colligative properties of solutions are properties that
depend upon the concentration of solute molecules or
ions, but not upon the identity of the solute. Colligative
properties include
1. freezing point depression: the difference between the
freezing point of a pure solvent and that of a solution.
2. boiling point elevation:the difference between the
boiling point of a solution and that of the pure solvent.
3.vapor pressure lowering, and osmotic pressure.

30. The concentration of the solute affects freezing
and boiling point changes: The more particles
there are the greater the freezing point
depression and the boiling point elevation.
Based on the number of moles of solute
particles produced, 1 mole of sodium chloride
is expected to be twice as effective dissolved
in water as 1 mol of sucrose,
C₁₂H₂₂O₁₁(s)H₂O-C₁₂H₂₂O₁₁ (aq)
NaCl(s)-H₂ONa
+
(aq)+Cl
-
(aq)

31. Emulsions
An emulsionis a mixture of two immiscible
substances. One substance is dispersed in the
other Examples of emulsions include butter
and margarine, espresso, mayonnaise, the
photo-sensitive side of photographic film, and
cutting fluid for metal working. In butter and
margarine, a continuous liquid phase
surrounds droplets of water (water-in-oil
emulsion). Emulsification is the process by
which emulsions are prepared.

32. Surfactant
What is soap?: A sodium or potassium salt of a
long chain fatty acid. If the skin has
accumulated oil dirt and bacteria then to
remove this one must first emulsify the oil by
scrubbing then stabilize it with an emulsifier
such as soap.
Only then can the soap and oily dirt emulsion
be rinsed away from the skin.

33. The soap ion dissolves the oil, forming a tiny
sphere called a micelle, while the other end on
the outside of the micelle dissolves in the
surrounding water. The oil droplet stays
suspended in the water and can be easily
washed away. The characteristic property of a
surfactant is its ability to form a layer between
two dissimilar phases.

34. Soap forms micelle which is the bubble.A thin
film of water is coated on both surfaces by
soap molecules.

35. Hard water destroys soap’s surfactant abilities.
Detergents outperform soaps in hard water.

36. Homework
Page 504
Term review all
Test prep all
Q.9 b
Q 10 all
Q.24 and 32 all