Conductance in Electrolytic Solutions.pptx

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1. CHEMISTRY PROJECT ON “ CONDUCTANCE OF ELECTROLYTIC SOLUTION” NAME - AYUSHI GUPTA CLASS – XII ROSE ROLL NO. – SUBJECT – CHEMISTRY SCHOOL – CHRIST JYOTI SENIOR SECONDARY SCHOOL, SATNA (M.P.) SUBMITTED TO – SUJA MAM

2. ACKNOWLEDGEMENT I under took this project work as part of our XII, I had tried to apply my best of knowledge and experience gain during the study in class work experience. I would like to extent my sincere thanks and gratitude to our MADAM MRS. SUJA ABRAHAM. She helped to understand and remember important details of my project. It has been successful only because of her guidance. AYUSHI GUPTA CLASS – XII (SCIENCE)

3. CERTIFICATE   This is to certify that AYUSHI GUPTA student of class - XII ROSE of CHRIST JYOTI SENIOR SECONDARY SCHOOL has successfully completed her project Work entitled “ CONDUCTANCE OF ELECTROLYTIC SOLUTION ” under my guidance. She has taken proper care and shown sincerity in completing the project. I certified that project is up to my expectation and as per the Guidance of CBSE. MRS. SUJA ABRAHAM Examiner:- Name: _______________ Signature:

4. PERMISSION LETTER To Mrs. Suja Christ Jyoti Higher Secondary School Satna (M.P.) Subject – To grant permission for preparing chemistry project Respected Madam, This letter is to get the permission from you for completing my project on CONDUCTANCE OF ELECTROLYTIC SOLUTION for annual examination of informatics practices under your guidance.   Thanking You Project Leader Project Mentor Name – Ayushi Gupta Mrs. Suja Abraham Roll No. -

5. TABLE OF CONTENT S. No. Topic Page No. 1 Conductance of electrolytic solution 1 2 Conductance of electrolyte 2 3 Specific conductivity 4 4 Equivalent conductivity 6 5 Molar conductivity 7 6 Relation between equivalent conductivity and molar conductivity 8 7 Conductivity cell 9 8 Wheatstone bridge 10 9 Koulraush law 12 10 Bibliography 15

6. Conductance in Electrolytic Solutions Electrolytes and nonelectrolytes are two types of water-soluble compounds. Electrolytes are electrovalent compounds that create ions in solution. Due to this, electrolytes conduct an electric current in the solution. Electrolytes include sodium chloride, copper (II) sulphate, and potassium nitrate. Nonelectrolytes, on the other hand, are covalent compounds that provide neutral molecules in solution. Nonelectrolytes do not conduct electricity. Nonelectrolytes include sugar, alcohol, and glycerol. As a result of the passage of electric current through its solution, an electrolyte invariably experiences chemical decomposition . The conductance of electricity by ions present in solutions is called electrolytic conductance or ionic conductance. Conductivity of electrolytic solution depends on following factors: Nature of electrolyte Size of ions produced and their solution Concentration of electrolyte Temperature (conductance increases with increase in temperature) 1

7. Conductance of Electrolytes Electrolyte solutions conduct electric currents by allowing ions to flow between electrodes. Conductivity, or conductance, is the ability of electrolytes to conduct electric currents. Electrolytes, like metallic conductors, follow Ohm’s law. The following relation provides the current I passing through a metallic conductor according to this law. I=E/R Where, E  is the potential difference between two points (in volts), and  R  denotes the resistance in ohms (or  Ω ). A conductor’s resistance  R  is proportional to its length,  l , and inversely proportional to its cross-sectional area ,  A. That is, R ∝ l/A Or R = ρ × l/A ……(1) 2

8. ρ  “rho” is a proportionality constant known as resistivity or specific resistance. Its value is determined by the conductor’s material. We can write from  (1): ρ = R×A/l If  l=1 cm  A=1 sq.cm,  then: ρ = R As a result, a conductor’s specific resistance is defined as the resistance in ohms that one-centimeter cube of it provides to the passage of electricity . 3

9. Specific Conductivity It is self-evident that a substance with a low resistance to current flow allows more current to travel through it . Thus, conductance, or the ability of a substance to conduct electricity, is the inverse of resistance . The reciprocal of specific resistance is known as Specific conductivity or conductivity . It is defined as the conductance of a solution of an electrolyte in a centimetre cube (cc). The specific conductivity is denoted by the symbol k (kappa). Thus, k = 1/ρ = 1/R × 1/k l/A known as cell constant. 4

10. Units of Specific Conductivity In general, conductance is measured in reciprocal ohms ( r.o ), mhos, or Ohm -1 . The following formula can be used to calculate its unit: k=1/A × 1/R × l/ohm × cm/cm2 ohm –1 cm –1 Variation of Specific Conductivity with Concentration Specific conductivity is the conductivity due to the ions present in 1cc of the solution. Therefore, as the concentration increases, specific conductivity increases. 5

11. Equivalent Conductivity It is the conducting power of all the ions furnished by one gm equivalent of an electrolyte present in a definite volume of solution. It is represented by  Λ eq . When concentration is changed, the number of ions present in 1 cc  of the solution also changes, and consequently conductivity of the solution changes . Λ eq = K/ C eq k =  Specific conductivity,  C eq =  Concentration of the solution in gm eq /unit volume Λ eq = k  . V eq ( Vm = Volume in  cc  of the solution containing one gm equivalent of electrolyte .) V eq = 1000/N [N=Normality] Λ eq = K . 1000/N Unit = ohm –1 cm 2 eq –1 or Scm 2 eq –1 6

12. Molar Conductivity It is the conducting power of all the ions furnished by one mole of an electrolyte present in a definite volume of the solution. It is represented by  Λ m . Λ m = k/C m C m =  The molar concentration of the solution Λ m = k.V m   ( V m =  Volume in  cc  of the solution containing  1mol  of electrolyte.) Λ m = k.1000/M   (M = Molar concentration) Unit : Ω -1 cm 2 mol –1  Or  S cm 2 mol -1 . 7

13. Relationship Between Molar Conductivity and Equivalent Conductivity Λ m / Λ eq = k/k × 1000/M × N/1000 = N/M Λ m / Λ eq = Molar mass / Equivalent mass Measurement of Electrolytic Conductivity The conductance of a solution is the reciprocal of its resistance. Therefore electrolytic conductivity of a solution can be measured by measuring the resistance of the solution. The resistance of an electrolytic solution is measured by using a special type of cell known as Conductivity Cell and a Wheatstone Bridge . 8

14. Conductivity Cell The glass apparatus used for measuring the resistance of a definite volume of a solution is called a conductivity cell . It is made of Pyrex glass and is fitted with two platinum electrodes fixed at a certain distance from each other. Conductivity cells are of different types. Some commonly used conductivity cells are shown in Figure. 9

15.  In a conductivity cell, the distance l between the two electrodes and the area  A  of the electrodes are fixed. Therefore, the quantity  l/A  is a constant for a particular conductivity cell. This quantity is termed cell constant. Thus , Cell Constant = l/A The unit of Cell Constant is cm -1 . Wheatstone Bridge Wheatstone Bridge is an important device used for the measurement of the resistance of a wire or of an electrolytic solution. It consists of four arms having resistances  R 1 , R 2 , R 3 and   R x  connected together through a galvanometer  Vo,  a battery  V EX  as shown in Figure . Resistance  R 2  is variable, while resistance  R x  is an unknown, i.e., whose value is to be measured. 10

16. Resistances R 1  and R 3  are known. After completing the circuit with the help of key K, the variable resistance R 2  is adjusted in such a way that a null point is obtained i.e., there is no deflection in the galvanometer. At this stage, according to the Wheatstone Bridge Principle R 1 /R x = R 2 /R 3 Or R x R 1 R 3 / R 2 Knowing the values R 1 ,R 2  and R 3 , the value of unknown resistance R x  can be determined. Limiting Molar Conductivity The molar conductivity of a solution at infinite dilution is known as limiting molar conductivity. 11

17. Kohlrausch Law Kohlrausch Law relates to the limiting molar conductivity of an electrolyte to its constituent ions. It basically states that the limiting molar conductivity of an electrolyte is equal to the sum of individual limiting molar conductivities of the cations and anions which make up the electrolyte. This law is also popularly known as the Kohlrausch Law of Independent Migration. Kohlrausch law and its applications are very important in the study of dilute solutions and also in the study of electrochemical cells. This law is mainly used to find the limiting conductivity of a weak electrolyte, among other important applications.  12

18. An example of this law is the limiting conductivity of sulphuric acid(H 2 SO 4 ). The limiting molar conductivity of sulphuric acid is equal to the sum of the limiting conductivities of hydrogen cation and sulphate anion.  The mathematical representation of the above statement is, λ ∞ H2SO4 = 2 λ ∞ H + + λ ∞ SO2−4 Here, λ∞ is the limiting molar conductivity. Applications of Kohlrausch Law - It is used to calculate the dissociation constant of an electrolyte. - It is used to calculate the limiting molar conductivity of a weak V electrolyte. - The degrees of dissociation of weak electrolytes are also found V using this law. 13

19. - Solubility constants of various salts are also calculated using this V law. - It is also used in the calculation of the cell potential in various V electrochemical cells 14

20. BIBLIOGRAPHY I Ayushi Gupta of class XII Rose, have completed this project file with the help of my subject teacher. I used the following links and books to finalise my file:- http://www.byjus.com/ http://www.toppers.com/ NCERT TEXTBOOK 15