Question

The commercial aluminum $($ trivalent, atomic wt. 27 $)$ is generally obtained by electrolysis of $AlC{l}_3$. The charges required to deposit 13.5 g of aluminum is

• A. 0.5 F
• B. 1.0 F
• C. 1.5 F
• D. 2.0 F

Answer 1

The correct option is C 1.5 F

Given

Atomic mass number of aluminium is $Z=27$

Valency of the aluminium is $v=3$

According to Faraday's first law, the mass of the substance deposited on an electrode during electrolysis is directly proportional to the quantity of electric charge passed through the electrolyte.

Now, we know one Faraday charge is required to deposit an equivalent mass,

$z$ of a substance given as

$z=\frac{Z}{v}$

$z=\frac{27}{3}=9g$

Also,

$m=zIt=zq$

Hence, the charge required to deposit 13.5 g of aluminium is

$q=\frac{13.5}{z}=\frac{13.5}{9}=1.5F$