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Electrochemistry · Question 63

AIPMT 2003MCQMedium📈 Topic in 38% papers+4−1
1

On the basis of the information available from the reaction, 4/3 Al + O2 2/3 Al2O3, G = -827 kJ mol-1 of O2, the minimum e.m.f. required to carry out an electrolysis of Al2O3 is ( F = 96500 C mol-1)

  1. 2.14 V
  2. 4.28 V
  3. 6.42 V
  4. 8.56 V

Answer

(1) 2.14 V

Solution

In Al2O3, Al is +3. Electrons transferred for 43 mol Al (per mol O2):

n = 43 3 = 4

For electrolysis (reverse reaction) G = +827 kJ and G = nFE

E = GnF

= 827 1034 96500

= 2.14 V

Answer: (1)

AIPMT 2003

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2

In electrolysis of NaCl when Pt electrode is taken then H2 is liberated at cathode while with Hg cathode it forms sodium amalgam because

  1. Hg is more inert than Pt
  2. more voltage is required to reduce H+ at Hg than at Pt
  3. Na is dissolved in Hg while it does not dissolve in Pt
  4. concentration of H+ ions is larger when Pt electrode is taken
AIPMT 2002
3

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.
AIPMT 2001
4

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
5

Cell reaction is spontaneous when

  1. is negative
  2. is positive
  3. E red is positive
  4. E red is negative
AIPMT 2000
6

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
7

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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