Question

The above fuel cell is used completely as an electrolytic cell with Cu voltmeter of resistance 26.94 $\Omega$ using Pt electrodes. Initially, Cu voltmeter contains 1 litre solution of 0.05M $CuS{O}_4$. Find $\left[H^{+}\right]$ in solution after electrolysis. (Assuming no change in volume of solution and e.m.f. of fuel cell to be constant over its usage)

• A. 0.015 M
• B. 0.03 M
• C. 0.025 M
• D. 0.01 M

Answer 1

Answer: (A)

0.015 M

$i=\frac{V}{R}=\frac{1.3}{26.94}=0.04825A.$
Time of electrolysis $=\frac{n_{O_2}}{r_{O_2}}=\frac{5}{10\times {10}^{-3}}=500$ minutes.
$C{u}^{2+}\left(aq\right)+H_{2}O\to Cu\left(s\right)+\frac{1}{2}{O}_2+2H^{+}\left(aq\right)$
$\therefore$ Moles of $H^{+}$ formed $=\frac{i\times t}{F}=\frac{0.04825\times 500\times 60}{96500}=0.015M$.