How much current is needed to pass for 1 sec for depositing a metal with a mass equal to double of its electrochemical equivalent?
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → 2 amp
By Faraday’s first law, the mass of a substance deposited at an electrode is proportional to the charge passed:
\( \displaystyle m = Z\,Q = Z\,I\,t \)
The constant Z is the electrochemical equivalent: the mass deposited by 1 coulomb, that is, by a current of 1 A flowing for 1 s. Here the mass deposited is twice the electrochemical equivalent, \( m = 2Z \), and t = 1 s:
\( \displaystyle 2Z = Z \times I \times 1\ \mathrm{s} \)
\( \displaystyle I = 2\ \mathrm{A} \)
So a current of 2 A is needed.
Shortcut: One electrochemical equivalent needs 1 C; two need 2 C, and 2 C in 1 s is 2 A.