Question

A steady current of $1.5\, A$ flows through a copper voltameter for 10 min. If the electrochemical equivalent of copper is $30 \times 10^{-5}\, g\, C ^{-1}$, the mass of copper deposited on the electrode will be

• A. 0.40 g
• B. 0.50 g
• C. 0.67 g
• D. 0.27 g

Answer 1

Answer: (D)

0.27 g

Answer 2

If $m$ is the mass of a substance deposited or liberated at an electrode during electrolysis when a charge $q$ passes through electrolyte, then according to Faraday's first law of electrolysis,
$m \propto q$
or $m=z q$
where $z$ is a constant of proportionality and is called electrochemical equivalent (ECE) of the the substance.
If an electric current $I$ flows through the electrolyte, then
$q =I t$
$\therefore m =z i t$
Here, $i=1.5 A , t =10\, \min =10 \times 60\, s,$
$z =30 \times 10^{-5} gC ^{-1}$
Hence, mass of copper deposited on the electrode
$m =30 \times 10^{-5} \times 1.5 \times 10 \times 60$
$=27 \times 10^{-2}=0.27\, g$