Question

During electrolysis, 25 g of a metal is deposited on the cathode of a metal nitrate solution by a current of 5 A passing for 4 hours. If the atomic weight of the metal is 100 amu, find the valency of the metal in the metal nitrate:

• A. 1
• B. 2
• C. 3
• D. 4

Answer 1

The correct option is C 3

Let the valency of the metal be n
Using Faraday's law of electrolysis,
$w=\frac{E.i.t}{F}$
Given,
w = 25 gm ; i = 5 A ; t = 4 hrs = $4\times 3600$ seconds
E = $\frac{atomicmass}{valency}=\frac{100}{n}$
put up the values,
25 =$\frac{\frac{100}{n}\times 5\times 4\times 3600}{96500}$
solving for n we get n= 3