#### Electro Chemistry Model Question Paper

12th Standard EM

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Chemistry

Time : 01:00:00 Hrs
Total Marks : 40
5 x 1 = 5
1. The number of electrons that have a total charge of 9650 coulombs is

(a)

6.22 ×1023

(b)

6.022 ×1024

(c)

6.022 ×1022

(d)

6.022 ×10−34

2. Faradays constant is defined as

(a)

charge carried by 1 electron

(b)

charge carried by one mole of electrons

(c)

charge required to deposit one mole of substance

(d)

charge carried by 6.22 ×1010 electrons

3. Which of the following electrolytic solution has the least specific conductance

(a)

2N

(b)

0.002N

(c)

0.02N

(d)

0.2N

4. Which of the statements about electrolytic conductance is not true?

(a)

Conductivity increases with decrease in viscosity.

(b)

Higher dielectric constant shows lower conductance in solution.

(c)

Temperature increases, conductance also increases.

(d)

Molar conductance increases with increase in dilution.

5. What happens during the electrolysis of molten sodium chloride?

(a)

Cl2 is released at the cathode

(b)

Liquid sodium is obtained at the anode

(c)

The emf of the overall reaction is -4.07 V

(d)

Cl2 is released at the cathode and Liquid sodium is obtained at the anode

6. 5 x 2 = 10
7. State Kohlrausch Law. How is it useful to determine the molar conductivity of weak electrolyte at infinite dilution.

8. A conductivity cell has two platinum electrodes separated by a distance 1.5 cm and the
cross sectional area of each electrode is 4.5 sq cm. Using this cell, the resistance of 0.5 N electrolytic solution was measured as 15 Ω . Find the specific conductance of the solution.

9. Give a mathematical expression that relates I cell constant, specific conductance and specific resistance.

10. Derive the unit of specific conductance.

11. Give the empirical relationship between molar conductance and concentration of the electrolyte.

12. 5 x 3 = 15
13. 0.1M NaCl solution is placed in two different cells having cell constant 0.5 and 0.25cm-1 respectively. Which of the two will have greater value of specific conductance.

14. Reduction potential of two metals M1 and M2 are $E^{0}_{M^{2+}_{1}|M_{1}} = -2.3V$ and $E^{0}_{M^{2+}_{1}|M_{1}} = 0.2V$ Predict which one is better for coating the surface of iron. Given: $E^{0}_{Fe^{2+}|Fe} = -0.44$V.

15. Answer the following question with regard to specific resistance.
(i) How is specific resistance represented?
(ii) What does specific resistance depend on?
(iii) What is the reciprocal of specific resistance? How is it denoted.
(iv) What is the unit of resitivity?

16. Write the reactions taking place in anode and cathode of a mercury button cell. Give the over all redox reaction of the cell with the emf generation