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1

### 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.
2

### 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
3

### 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.
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

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Class 12