Question

What current is passed for $0.25$ seconds for deposition of certain weight of metal which is equal to its electrochemical equivalent?
(A) $4A$
(B) $100A$
(C) $200A$
(D) $2A$

Answer 1

Hint : Use faraday’s laws of electrolysis. It’s first law states that the amount of substance deposited is the product of electrochemical equivalent of metal, current passing through the metal and time for which the current is passed.

Complete Step By Step Answer:
Let $W$ be the amount or weight of metal deposited, $I$ be the current flowing through the metal, $t$ be the time in seconds and $Z$ be the electrochemical equivalent.
According to the faraday’s first law of electrolysis, we have
$W = ZIt$ …. $(1)$
But in the question it has been mentioned that the weight of metal deposited is equal to the electrochemical equivalent of the metal.
$\Rightarrow W = Z$
Therefore, from $(1)$ , we get
$\dfrac{W}{Z} = 1 \Rightarrow 1 = I \times t$ ……( $t = 0.25s$ …given)
$\therefore I = \dfrac{1}{{0.25}}$
$\Rightarrow I = 4A$
Thus, we have reached the answer of the question that current is $4A$ .
Correct option is A.

Note :
Here the main concept we have used is the faraday’s 1st law of electrolysis. Just remember the concept and apply it whenever we have been given this type of problem. The perk here was that weight and equivalent are equal. Thus we found out the current flowing in time $t = 0.25s$ .