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1

### NEET 2016 Phase 2

MCQ (Single Correct Answer)
If the Eocell for a given reaction has a negative value, which of the following gives the correct relationships for the values of $$\Delta$$Go and Keq ?
A
$$\Delta$$Go > 0;   Keq < 1
B
$$\Delta$$Go > 0;   Keq > 1
C
$$\Delta$$Go < 0;   Keq > 1
D
$$\Delta$$Go < 0;   Keq < 1

## Explanation

We know that

$$\Delta$$Go = –nFEocell

Eocell = -ve then $$\Delta$$Go = +ve or $$\Delta$$Go > 0

$$\Delta$$Go = -nRTlog Keq

For $$\Delta$$Go = +ve, Keq = -ve or Keq < 1.
2

### NEET 2016 Phase 2

MCQ (Single Correct Answer)
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
3

### NEET 2016 Phase 2

MCQ (Single Correct Answer)
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
4

### NEET 2016 Phase 2

MCQ (Single Correct Answer)
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.

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NEET

Class 12