1

### NEET 2016 Phase 2

During the electrolysis of molten sodium chloride, the time required to produce 0.10 mol of chlorine gas using a current of 3 amperes is
A
55 minutes
B
110 minutes
C
220 minutes
D
330 minutes

## Explanation

At cathode : 2Na+ + 2e $\to$ 2Na

At anode : 2Cl $\to$ Cl2 + 2e
----------------------------------------------

Net reaction: 2Na+ + 2Cl $\to$ 2Na + Cl2

From Faraday’s first law of electrolysis,

w = Z$\times$I$\times$t

= ${E \over {96500}}$$\times$I$\times$t

No. of moles of Cl2 gas × Mol. wt. of Cl2 gas

= ${{Eq.\,wt.\,of\,C{l_2}\,gas \times I \times t} \over {96500}}$

$\Rightarrow$ 0.10 $\times$ 71 = ${{35.5 \times 3 \times t} \over {96500}}$

$\Rightarrow$ t = ${{0.10 \times 71 \times 96500} \over {35.5 \times 3}}$

= 6433.33 sec

= 107.22 min $\simeq$ 110 min
2

### NEET 2016 Phase 2

The number of electrons delivered at the cathode during electrolysis by a current of 1 ampere in 60 seconds is (charge on electron = 1.60 $\times$ 10$-$19C)
A
6 $\times$ 1023
B
6 $\times$ 1020
C
3.75 $\times$ 1020
D
7.48 $\times$ 1023

## Explanation

Q = I × t

Q = 1 × 60 = 60 C

Now, 1.60 × 10–19 C $\equiv$ 1 electron

$\therefore$ 60 C $\equiv$ ${{60} \over {1.6 \times {{10}^{ - 19}}}}$

= 3.75 $\times$ 1020 electrons
3

### NEET 2016 Phase 2

Zinc can be coated on iron to produce galvanized iron but the reverse is not possible. It is because
A
zinc is lighter than iron
B
zinc has lower melting point than iron
C
zinc has lower negative electrode potential than iron
D
zinc has higher negative electrode potential than iron

## Explanation

The reduction potential values are

Zn2+/Zn = – 0.76 V

Fe2+/Fe = – 0.44 V

Thus, due to higher negative electro potential value of zinc than iron, iron cannot be coated on zinc.
4

### 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