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#### Electro Chemistry Model Question Paper 1

12th Standard EM

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Chemistry

Time : 01:00:00 Hrs
Total Marks : 50
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. The molar conductivity of a 0.5 mol dm-3 solution of AgNO3 with electrolytic conductivity of 5.76 ×10−3 S cm−1at 298 K is

(a)

2.88 S cm2mol-1

(b)

11.52 S cm2mol-1

(c)

0.086 S cm2mol-1

(d)

28.8 S cm2 mol -1

3. A current strength of 3.86 A was passed through molten Calcium oxide for 41minutes and 40 seconds. The mass of Calcium in grams deposited at the cathode is (atomic mass of Ca is 40g / mol and 1F = 96500C).

(a)

4

(b)

2

(c)

8

(d)

6

4. Zinc can be coated on iron to produce galvanized iron but the reverse is not possible. It is because

(a)

Zinc is lighter than iron

(b)

Zinc has lower melting point than iron

(c)

Zinc has lower negative electrode potential than iron

(d)

Zinc has higher negative electrode potential than iron

5. In H2-Ofuel cell the reaction occur at cathode is

(a)

O2(g) + 2H2O (l) + 4e- ⟶ 4OH (aq)

(b)

H+(aq) + OH (aq) ⟶ H2O (l)

(c)

2H2 (g) + O (g) ⟶ 2H2O (g)

(d)

H+ + e-+ ⟶ 1/2 H2

6. 5 x 2 = 10
7. Define anode and cathode

8. State Faraday’s Laws of electrolysis

9. The resistance of a conductivity cell is measured as 190 Ω using 0.1M KCl solution (specific conductance of 0.1M KCl is 1.3 Sm-1) . When the same cell is filled with 0.003M sodium chloride solution, the measured resistance is 6.3KΩ. Both these measurements are made at a particular temperature. Calculate the specific and molar conductance of NaCl solution. Given that

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

11. Account for the following : For a strong electrolyte molar conductivity decreases as concentration increases

12. 5 x 3 = 15
13. Why is AC current used instead of DC in measuring the electrolytic conductance?

14. 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.

15. A solution of silver nitrate is electrolysed for 20 minutes with a current of 2 amperes. Calculate the mass of silver deposited at the cathode.

16. From the below graph. Explain the variation of molar conductance of a weak electrolyte with decrease in concentration.

17. How are electro chemical cells classified? Explain.

18. 4 x 5 = 20
19. 0.1M copper sulphate solution in which copper electrode is dipped at 250C . Calculate the electrode potential of copper. [Given: E0Cu2+|Cu=0.34].

20. For the cell Mg (s) Mg2+(aq)||Ag2+(aq)|Ag(s), calculate the equilibrium constant at 250C and maximum work that can be obtained during operation of cell. Given : $E^{0}_{Mg^{2+}|Mg}$=-237V and $E^{0}|_{Ag^{2+}|Ag}$=0.80V.

21. Specific conductance of 1M KNO3 solution is oberved to be 5.55 x 10-3 mho cm2. What is the equivalent conductance of KNO3 when one litre of the solution is used?

22. How will you calculate solubility product of AgCI which is a sparingly soluble salt?