1)

How many Faradays of electricity are required to deposit 10 g of calcium from molten calcium chloride using inert electrodes? (Molar mass of calcium=40g $mol^{-1}$)


A) 0.5 F

B) 1 F

C) 0.25 F

D) 2 F

Answer:

Option A

Explanation:

Relationship  obtained on combining Faraday's first and second laws.

$W=ZQ=\frac{E}{F}\times Q= \frac{Q}{F}\times E= \frac{Q}{F}\times \frac{N}{z}$

$=\frac{l\times t}{F}\times \frac{M}{z}$

 Here, Z= electrochemical equivalent

Q= quantity of electricity passed

M= atomic mass

z= valency of the metal

 F= one Faraday or 96500 C

Given, weight  of calcium that has to be deposited=10 g

 z of the metal ion=2

 Molecular mass of calcium =40 g mol-1

 $W=\frac{l. T}{F}\times \frac{M}{z}; 10=\frac{l. T}{F}\times \frac{40}{2}$

$=\frac{10\times2}{40}F=IT\Rightarrow 0.5F=l.T$