1

### NEET 2016 Phase 2

The molar conductivity of a 0.5 mol/dm3 solution of AgNO3 with electrolytic conductivity of 5.76 $\times$ 10$-$3 S cm$-$1 at 298 K is
A
2.88 S cm2/mol
B
11.52 S cm2/mol
C
0.086 S cm2/mol
D
28.8 S cm2/mol

## Explanation

${\Lambda _m} = {{\kappa \times 1000} \over {Molality}}$

= ${{5.76 \times {{10}^{ - 3}} \times 1000} \over {0.5}}$

= 11.52 S cm2/mol
2

### AIPMT 2015 Cancelled Paper

A device that converts energy of combustion of fuels like hydrogen and methane, directly into electrical energy is known as
A
dynamo
B
Ni-Cd cell
C
fuel cell
D
electrolytic cell

## Explanation

A device that converts energy of combustion of fuels, directly into electrical energy is known as fuel cell.
3

### AIPMT 2014

The weight of silver (at. wt. = 108) displaced by a quantity of electricity which displaces 5600 mL of O2 at STP will be
A
5.4 g
B
10.8 g
C
54.0 g
D
108.0 g

## Explanation

We know, from Faraday’s second law

${{{W_{Ag}}} \over {{E_{Ag}}}} = {{{W_{{O_2}}}} \over {{E_{{O_2}}}}}$

$\Rightarrow$ ${{{W_{Ag}}} \over {108}} = {{{{5600} \over {22400}} \times 32} \over 8}$

$\Rightarrow$ ${{{W_{Ag}}} \over {108}} = {8 \over 8}$

$\Rightarrow$ ${{W_{Ag}} = 108}$ g
4

### AIPMT 2014

When 0.1 mol MnO$_4^{2 - }$ is oxidised the quantity of electricity required to completely oxidise MnO$_4^{2 - }$ to MnO$_4^ -$ is
A
96500 C
B
2 $\times$ 96500 C
C
9650 C
D
96.50 C

## Explanation

$\mathop {MnO_4^{2 - }}\limits_{0.1\,mole}^{ - 6}$ $\to$ $\mathop {MnO_4^ - }\limits^{ - 7}$ + e-

Quantity of electricity required = 0.1F

= 0.1 × 96500 = 9650 C