Electrochemistry

A device that converts energy of combustion of fuels like hydrogen and methane, directly into electrical energy is known as

1. dynamo
2. Ni-Cd cell
3. fuel cell
4. electrolytic cell

When 0.1 mol MnO42- is oxidised the quantity of electricity required to completely oxidise MnO42- to MnO4- is

1. 96500 C
2. 2 96500 C
3. 9650 C
4. 96.50 C

The weight of silver (at. wt. = 108) displaced by a quantity of electricity which displaces 5600 mL of O2 at STP will be

1. 5.4 g
2. 10.8 g
3. 54.0 g
4. 108.0 g

At 25 C molar conductance of 0.1 molar aqueous solution of ammonium hydroxide is 9.54 ohm-1 cm2 mol-1 and at infinite dilution its molar conductance is 238 ohm-1 cm2 mol-1. The degree of ionisation of ammonium hydroxide at the same concentration and temperature is

1. 4.008\%
2. 40.800\%
3. 2.080\%
4. 20.800\%

A button cell used in watches functions as follows. Zn(s) + Ag2O(s) + H2O(l) 2Ag(s) + Zn2+(aq) + 2OH-(aq) If half cell potentials are Zn2+(aq) + 2e- Zn(s); E = -0.76 V Ag2O(s) + H2O(l) + 2e- 2Ag(s) + 2OH-(aq), E = 0.34 V The cell potential will be

1. 0.84 V
2. 1.34 V
3. 1.10 V
4. 0.42 V

A hydrogen gas electrode is made by dipping platinum wire in a solution of pH = 10 and by passing hydrogen gas around the platinum wire at one atm pressure. The oxidation potential of electrode would be

1. 0.118 V
2. 1.18 V
3. 0.059 V
4. 0.59 V

Consider the half-cell reduction reaction Mn2+ + 2e- Mn, E = -1.18 V Mn2+ Mn3+ + e-, E = -1.51 V The E for the reaction 3Mn2+ Mn + 2Mn3+, and possibility of the forward reaction are respectively

1. -4.18 V and yes
2. +0.33 V and yes
3. +2.69 V and no
4. -2.69 V and no

How many gram of cobalt metal will be deposited when a solution of cobalt (II) chloride is electrolyzed with a current of 10 amperes for 109 minutes ( 1 Faraday = 96,500 C; Atomic mass of Co = 59 u)

1. 4.0
2. 20.0
3. 40.0
4. 0.66

Standard reduction potentials of the half reactions are given below : F2(g) + 2e- 2F-(aq); E = +2.85 V Cl2(g) + 2e- 2Cl-(aq); E = +1.36 V Br2(l) + 2e- 2Br-(aq); E = +1.06 V I2(s) + 2e- 2I-(aq); E = +0.53 V The strongest oxidising and reducing agents respectively are

1. F2 and I-
2. Br2 and Cl-
3. Cl2 and Br-
4. Cl2 and I2

Molar conductivities ( m) at infinite dilution of NaCl, HCl and CH3COONa are 126.4, 425.9 and 91.0 S cm2 mol-1 respectively. ( m) for CH3COOH will be

1. 425.5 S cm2 mol-1
2. 180.5 S cm2 mol-1
3. 290.8 S cm2 mol-1
4. 390.5 S cm2 mol-1