#### 12th Standard Chemistry English Medium Electro Chemistry Reduced Syllabus Important Questions 2021

12th Standard

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Chemistry

Time : 01:00:00 Hrs
Total Marks : 100

Multiple Choice Questions

15 x 1 = 15
1. Which of the following electrolytic solution has the least specific conductance

(a)

2N

(b)

0.002N

(c)

0.02N

(d)

0.2N

2. 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

3. The equivalent conductance of M/36solution of a weak monobasic acid is 6mho cm2 and at infinite dilution is 400 mho cm2. The dissociation constant of this acid is

(a)

1.25 ×10−6

(b)

6.25 x 10-6

(c)

1.25 ×10−4

(d)

6.25 x 10 -5

4. A conductivity cell has been calibrated with a 0.01M, 1:1 electrolytic solution (specific conductance ( k =1.25x10-3cm-1) in the cell and the measured resistance was 800 Ω at 25oC. The cell constant is,

(a)

10−1 cm−1

(b)

101 cm−1

(c)

1 c m−1

(d)

5.7x10-12

5. Kohlraush's law is applied to calculate

(a)

molar conductance at infinite dilution of a weak electrolyte

(b)

degree of dissociation of weak electrolyte

(c)

solubility of a sparingly soluble salt

(d)

all the above

6. The specific conductance of a 0.01 M solution of KCI is 0.0014 ohm-1 em-1 at 25°C. Its equivalent conductance is

(a)

14 ohm-1 cm2eq-1

(b)

140 ohm-1 cm2eq-1

(c)

1.4 ohm-1 cm2eq-1

(d)

0.14 ohm-1 cm2eq-1

7. The equivalent conductivity of CH3COOH at 25°C is 80 ohm-1 cm2 eq-1 and at infmite dilution 400 ohm-1 cm-1 eq-1. The degree of dissociation of CH3COOH is

(a)

1

(b)

0.2

(c)

0.1

(d)

0.3

8. The important use of Kohlrausch's law is deducing the

(a)

λ value of weak electrolyte.

(b)

λ value of strong electrolyte.

(c)

λ value of weak electrolyte.

(d)

λ value of weak electrolyte

9. According to Faraday's first law m = ZIt, where Z is

(a)

reaction quotient

(b)

effective nuclear charge

(c)

atomic number

(d)

electrochemical equivalent

10. Which among the following has same equivalent and molar conductance

(a)

H2SO4

(b)

CH3COOH

(c)

NaCI

(d)

Na2SO4

11. Ionic conductance at infmite dilution of Al3+ and SO2-4 are 1890 ohm-1 cm2 gm equiv-1 and 1600 ohm-1 cm-2 gm equiv-1 respectively. The equivalent conductance is

(a)

143 mho cm2 gm equiv-1

(b)

850 mho cm2 gm equir-1

(c)

153 mho cm2 gm equiv-1

(d)

314 mho cm2 gm equir-1

12. Which of the following statement is wrong with regard to galvanic cell?

(a)

Reduction takes place at cathode

(b)

Reduction takes place at anode

(c)

Oxidation takes place at anode

(d)

Cathode is positively charged

13. Standard electrode potential of Sn4+ / Sn2+  couple is +0.15 V and that of Cr3+ / Cr is 0.85 V. When connected, the cell potential will be

(a)

1.10 V

(b)

1.00 V

(c)

0.70 V

(d)

0.30 V

14. The cell in which electrical energy is used to bring about chemical change is known as _______

(a)

electrolyticcell

(b)

galvaniccell

(c)

voltaic cell

(d)

dynamo

15. The feasibility of a redox reaction can be predicted with the help of ________

(a)

reduction potential

(b)

oxidation potential

(c)

electrochemical series

(d)

standard emf

1. 2 Marks

10 x 2 = 20
16. State Kohlrausch Law. How is it useful to determine the molar conductivity of weak electrolyte at infinite dilution.

17. Why is anode in galvanic cell considered to be negative and cathode positive electrode?

18. 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.

19. On dilution of 0.1 M of Na2SO4, what will happen to its
a) Conductance (C)
(b) Conductivity K
(c) Molar conductance Am
(d) Equivalent conductance ${ \Lambda }_{ m }$

20. Apply Kohlraush's law and determine the limiting molar conductivity of
(i) BaCl2
(ii) AI2(SO4)3

21. What are the factors on which cell potential depends?

22. Higher the standard reduction potential lesser is corrosion. Give reason.

23. Define electrochemical equivalent

24. What is single electrode potential?

25. Write the Nernst equation.

1. 3 Marks

10 x 3 = 30
26. 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.

27. 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 : $\mathrm{E}_{\mathrm{Fe}^{2+} \mid \mathrm{Fe}}^{\circ}=-0.44 \mathrm{~V}$

28. 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?

29. Define equivalent conductance.

30. How are electro chemical cells classified? Explain.

31. Give the oxidation and reduction half cell reaction taking place in the Daniel cell.

32. Write the cell representation of the galvanic cell in which the following reaction take place
${ Zn }_{ (s) }+Cu{ SO }_{ 4 }\rightarrow { ZnSO }_{ 4 }+{ Cu }_{ (s) }$
For the above cell. Identify the anode and cathode half cell.

33. Explain the IUPAC convention of representing a Galvanic cell

34. Leclanche cell is a non-rechargeable cell. Answer the questions below with respect to Leclanche cell.
(i) Anode
(ii) Cathode
(iii) Electrolyte
(iv) Oxidation half cell reaction
(v) Reduction half cell reaction.

35. Define Faraday.

1. 5 Marks

7 x 5 = 35
36.  Calculate the standard emf of the cell: Cd|Cd2+||Cu2+|Cu and determine the cell reaction. The standard reduction potentials of Cu2+|Cu and Cd2+|Cd  are 0.34V and -0.40 volts respectively. Predict the feasibility of the cell reaction.

37. Derive an expression for Nernst equation

38. The electrochemical equivalent of an electrolyte is 2.35 gm amp-1 sec-1. Calculate I the amount of the substance deposited when 5 ampere is passed for 10 sec.

39. 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?

40. The standard reduction potential for the reaction Sn4+ + 2e- ⟶ Sn2+ is + 0.15v. Calcuate the free energy change of the reaction.

41. Write the Nernst equation for the half cell Zn2+(aq)/ Zn(s)

42. How will you determine the conductivity of an electrolytic solution using a wheatstone , bridge?