Electrochemistry · Question 50

Al2O3 is reduced by electrolysis at low potentials and high currents. If 4.0 104 amperes of current is passed through molten Al2O3 for 6 hours, what mass of aluminium is produced? (Assume 100% current efficiency, at. mass of Al = 27 g mol-1).

1. 8.1 104 g
2. 2.4 105 g
3. 1.3 104 g
4. 9.0 103 g

The equivalent conductance of M/32 solution of a weak monobasic acid is 8.0 mho cm2 and at infinite dilution is 400 mho cm2. The dissociation constant of this acid is

1. 1.25 10-6
2. 6.25 10-4
3. 1.25 10-4
4. 1.25 10-5

On the basis of the following E values, the strongest oxidizing agent is [Fe(CN)6]4- [Fe(CN)6]3- + e-; E = -0.35 V Fe2+ Fe3+ + e-; E = -0.77 V

1. Fe3+
2. [Fe(CN)6]3-
3. [Fe(CN)6]4-
4. Fe2+

Kohlrausch's law states that at

1. Infinite dilution, each ion makes definite contribution to conductance of an electrolyte whatever be the nature of the other ion of the electrolyte
2. Infinite dilution, each ion makes definite contribution to equivalent conductance of an electrolyte, whatever be the nature of the other ion of the electrolyte
3. Finite dilution, each ion makes definite contribution to equivalent conductance of an electrolyte, whatever be the nature of the other ion of the electrolyte
4. Infinite dilution, each ion makes definite contribution to equivalent conductance of an electrolyte depending on the nature of the other ion of the electrolyte.

Standard free energies of formation (in kJ/mol) at 298 K are -237.2, -394.4 and -8.2 for H2O(l), CO2(g) and pentane (g) respectively. The value of E cell for the pentane-oxygen fuel cell is

1. 1.0968 V
2. 0.0968 V
3. 1.968 V
4. 2.0968 V

The equilibrium constant of the reaction: Cu(s) + 2Ag+(aq) Cu2+(aq) + 2Ag(s); E = 0.46 V at 298 K is

1. 2.0 1010
2. 4.0 1010
3. 4.0 1015
4. 2.4 1010

The efficiency of a fuel cell is given by

1. G/ S
2. G/ H
3. S/ G
4. H/ G

A hypothetical electrochemical cell is shown below. A | A+(xM) || B+(yM) | B The emf measured is + 0.20 V. The cell reaction is

1. A + B+ A+ + B
2. A+ + B A + B+
3. A+ + e- A; B+ + e- B
4. the cell reaction cannot be predicted.

E Fe2+/Fe = -0.441 V and E Fe3+/Fe2+ = 0.771 V, the standard EMF of the reaction Fe + 2Fe3+ 3Fe2+ will be

1. 0.111 V
2. 0.330 V
3. 1.653 V
4. 1.212 V

4.5 g of aluminium (at. mass 27 amu) is deposited at cathode from Al3+ solution by a certain quantity of electric charge. The volume of hydrogen produced at STP from H+ ions in solution by the same quantity of electric charge will be

1. 44.8 L
2. 22.4 L
3. 11.2 L
4. 5.6 L