Electrochemistry

EXERCISE-01 CHECK YOUR GRASP
SELECT THE CORRECT ALTERNATIVE (ONLY ONE CORRECT ANSWER)

1. If a spoon of copper metal is placed in a solution of ferrous sulphate :-
(A) Cu will precipitate out (B) iron will precipitate
(C) Cu and Fe will precipitate (D) no reaction will take place
2. During discharge of a lead storage cell the density of sulphuric acid in the cell :-
(A) increasing (B) decreasing
(C) remains unchanged (D) initially increases but decreases subsequently
3. Which of the following represents the reduction potential of silver wire dipped into 0.1 M AgNO3 solution at
25°C :-
(A) E°red (B) (E°red + 0.059) (C) (E°ox – 0.059) (D) (E°red – 0.059)
4. If the solution of the CuSO4 in which copper rod is immersed is diluted to 10 times, the electrode reduction
potential. (T = 298 K) :-
(A) increases by 0.030 volt (B) decreases by 0.030 volt
(C) increases by 0.059 volt (D) decreases by 0.0059 volt
5. The oxidation potential of a hydrogen electrode at pH = 1 is (T = 298 K) :-
(A) 0.059 volt (B) 0 volt (C) –0.059 volt (D) 0.59 volt
6. The electrode potential becomes equal to standard electrode potential when reactants and products concen-
tration ratio is :-
(A) equal to 1 (B) greater than 1 (C) less than 1 (D) none of the above
7. The reduction potential values are given below
Al3+ / Al = – 1.67 volt, Mg2+ / Mg = –2.34 volt Cu2+ / Cu = + 0.34 volt
I2 / 2l– = + 0.53 volt. Which one is the best reducing agent ?
(A) Al (B) Mg (C) Cu (D) I2
8. When iron is rusted, it is :-
(A) reduced (B) oxidised (C) evaporated (D) decomposed
9. The reference electrode is made from which of the following :-
(A) ZnCl2 (B) CuSO4 (C) Hg2Cl2 (D) HgCl2
10. Given standard electrode potentials :
Fe3+ + 3e–  Fe ; E° = –0.036 volt
Fe2+ + 2e–  Fe ; E° = –0.440 volt
The standard electrode potential E° for
Fe3+ + e–  Fe2+ is :-
(A) –0.476 volt (B) –0.404 volt (C) 0.440 volt (D) 0.772 volt
11. The reduction potential of a hydrogen electrode at pH 10 at 298 K is : (p = 1 atm)
(A) 0.51 volt (B) 0 volt (C) –0.591 volt (D) 0.059 volt
12. The emf of the cell, Ni|Ni (1.0 M)||Ag (1.0 M)|Ag[E° for Ni /Ni = – 0.25 volt, E° for Ag+/Ag = 0.80 volt]
2+ + 2+
is given by : [E° for Ag+ / Ag = 0.80 volt]

(A) –0.25 + 0.80 = 0.55 volt (B) –0.25 – (+0.80) = –1.05 volt
(C) 0 + 0.80 – (–0.25) = + 1.05 volt (D) –0.80 – (+0.25) = –0.55 volt
13. The position of some metals in the electrochemical series in decreasing electropositive character is given as
Mg > Al > Zn > Cu > Ag. What will happen if a copper spoon is used to stir a solution of aluminium nitrate?
(A) The spoon will get coated with aluminium (B) An alloy of aluminium and copper nitrate
(C) The solution becomes blue (D) There is no reaction
14. E° (Ni / Ni) = – 0.25 volt, E° (Au / Au) = 1.50 volt. The emf of the voltaic cell Ni|Ni2+ (1.0 M)||Au3+ (1.0
2+ 3+
M)| Au is :-
(A) 1.25 volt (B) –1.75 volt (C) 1.75 volt (D) 4.0 volt
15. When the electric current is passed through a cell having an electrolyte, the positive ions move towards
cathode and negative ions towards the anode. If the cathode is pulled out of the solution :-
(A) the positive and negative ions will move towards anode
(B) the positive ions will start moving towards the anode while negative ions will stop moving
(C) the negative ions will continue to move towards anode while positive ions will stop moving
(D) the positive and negative ions will start moving randomly
16. The oxidation potentials of Zn, Cu, Ag, H2 and Ni are 0.76, –0.34, –0.80, 0.00, 0.25 volt respectively.
Which of the following reactions will provide maximum voltage :-
(A) Zn + Cu2+  Cu + Zn2+ (B) Zn + 2Ag+  2Ag + Zn2+
(C) H2 + Cu2+  2H+ + Cu (D) H2 + Ni2+  2H+ + Ni
17. Which one of the following will increase the voltage of the cell : (T = 298 K)
Sn + 2 Ag+  Sn2+ + 2 Ag
(A) increase in the size of silver rod (B) increase in the concentration of Sn+2 ions
(C) increase in the concentration of Ag+ ions (D) none of the above
18. A chemist wants to produce Cl2 (g) from molten NaCl. How many grams could be produced if he uses a
steady current of 2 ampere for 2.5 minutes :-
(A) 3.55 g (B) 1.775 g (C) 0.110 g (D) 0.1775 g
19. Consider the reaction : (T = 298 K)
Cl2 (g) + 2Br– (aq)  2Cl– (aq) + Br2 (aq.)
The emf of the cell, when [Cl–] = [Br2] = [Br–] = 0.01 M and Cl2 gas is 1 atm pressure, will be (E° for the
above reaction is = 0.29 volt) :-
(A) 0.54 volt (B) 0.35 volt (C) 0.24 volt (D) –0.29 volt
20. Three faradays of electricity was passed through an aqueous solution of iron (II) bromide. The mass of iron
metal (at. mass 56) deposited at the cathode is :-
(A) 56 g (B) 84 g (C) 112 g (D) 168 g
21. The standard emf for the cell reaction Zn + Cu  Zn + Cu is 1.10 volt at 25°C. The emf for the cell
2+ 2+
reaction when 0.1 M Cu2+ and 0.1 Zn2+ solutions are used at 25°C is :-
(A) 1.10 volt (B) 0.110 volt (C) –1.10 volt (D) –0.110 volt
22. Three moles of electrons are passed through three solutions in succession containing AgNO3, CuSO4 and
AuCl3 respectively. The molar ratio of amounts of cations reduced at cathode will be :-
(A) 1 : 2 : 3 (B) 2 : 1 : 3 (C) 3 : 2 : 1 (D) 6 : 3 : 2
23. The emf of the cell involving the following reaction, 2 Ag+ + H2  2 Ag + 2H+ is 0.80 volt. The standard
oxidation potential of silver electrode is :-
(A) –0.80 volt (B) 0.80 volt (C) 0.40 volt (D) –0.40 volt
+ –
24. For the electrochemical cell, M|M ||X |X, E°M+/M = 0.44 V and E°X/X– = 0.33 V. From this data we can
deduce that :-
(A) M + X  M+ + X– is the spontaneous reaction
(B) M+ + X–  M + X is the spontaneous reaction
(C) Ecell = 0.77 V
(D) Ecell = –0.77 V
25. For the net cell reaction of the cell Zn(s)|Zn2+||Cd2+|Cd(s) G° in kilojules at 25°C is (E°cell = 0.360 V):-
(A) 112.5 (B) 69.47 (C) –34.73 (D) –69.47
– 2+
26. How many faradays are required to reduce one mol of MnO4 to Mn :-
(A) 1 (B) 2 (C) 3 (D) 5
27. Cu + e  Cu, E° = x1 volt ;
+ –
Cu2+ + 2e–  Cu, E° = x2 volt, then for

Cu2+ + e–  Cu+, E° (volt) will be :
(A) x1 – 2x2 (B) x1 + 2x2 (C) x1 – x2 (D) 2x2 – x1

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EXERCISE-01 CHECK YOUR GRASP

SELECT THE CORRECT ALTERNATIVE (ONLY ONE CORRECT ANSWER)

is given by : [E° for Ag+ / Ag = 0.80 volt]

Cu2+ + 2e–  Cu, E° = x2 volt, then for

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