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Electrochemistry · Question 65

AIPMT 2001MCQMedium📈 Topic in 12% papers+4−1
1

Standard electrode potentials are Fe2+/Fe [ E = -0.44 V] and Fe3+/Fe2+ [ E = 0.77 V]; If Fe2+, Fe3+ and Fe blocks are kept together, then

  1. Fe3+ increases
  2. Fe3+ decreases
  3. Fe2+/Fe3+ remains unchanged
  4. Fe2+ decreases.

Answer

(2) Fe3+ decreases

Solution

The couple with the lower reduction potential acts as anode (oxidation) and the one with the higher potential as cathode (reduction).

Anode: Fe Fe2+ + 2e-

Cathode: 2Fe3+ + 2e- 2Fe2+

E cell = E cathode - E anode

= 0.77 - (-0.44)

= 1.21 V

E cell is positive, so the reaction Fe + 2Fe3+ 3Fe2+ is spontaneous.

Fe3+ decreases (and Fe2+ increases).

Answer: (2)

AIPMT 2001

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2

The most convenient method to protect the bottom of ship made of iron is

  1. coating it with red lead oxide
  2. white tin plating
  3. connecting it with Mg block
  4. connecting it with Pb block
AIPMT 2001
3

Cell reaction is spontaneous when

  1. is negative
  2. is positive
  3. E red is positive
  4. E red is negative
AIPMT 2000
4

Ionic conductances of Ba2+ and Cl- ions at infinite dilution are 127 and 76 ohm-1 cm2 mol-1 respectively. Equivalent conductance of BaCl2 at infinite dilution is

  1. 139.5
  2. 101.5
  3. 203
  4. 279
AIPMT 2000
5

For the disproportionation of copper 2Cu+ Cu2+ + Cu, E is (Given E for Cu2+/Cu is 0.34 V and E for Cu2+/Cu+ is 0.15 V.)

  1. 0.49 V
  2. -0.19 V
  3. 0.38 V
  4. -0.38 V
AIPMT 2000

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