Question

W g of copper is deposited in a copper voltameter when an electric current of 2 ampere is passed for 2 hours. If one ampere of electric current is passed for 4 hours in the same voltameter, copper deposited will be:

• A. w
• B. w/2
• C. w/4
• D. 2 w

Answer 1

Answer: (A)

w

The cathodic reaction : ${Cu}^{2+}+2e^{-}⟶Cu$

$I_1=2$ amps and $t_1=2$ hrs $=2\times 3600$ secs $=7200$ secs

$Q_1=I_1{t}_1=2\times 7200C$

$2\times 7200C$ will deposit $=\frac{63.5\times 2\times 7200}{2\times 96500}=W$ gm of $Cu$

now, $I_2=1$ amp and $t_2=4$ hrs $=4\times 3600$ sec $=14400$ secs

$Q_2=I_2{t}_2=1\times 14400C$

$\therefore$ $1\times 14400C$ will deposit $=\frac{63.5\times 14400}{2\times 96500}=\frac{63.5\times 2\times 7200}{2\times 96500}$gm of $Cu$ $=$ w gm of $Cu$

$\therefore$ correct answer is $A$.