Question

The cell potential for the given cell at 298 K $\text{Pt} | \text{H}_2 \text{(g, 1 bar)} | \text{H}^+ \text{(aq)} || \text{Cu}^{2+} \text{(aq)} | \text{Cu(s)}$ is 0.31 V. The pH of the acidic solution is found to be 3, whereas the concentration of Cu2+ is 10–x M. The value of x is _____.
(Given : $E^{Θ}_{Cu^{2+}/Cu}$ = 0.34 V and $\frac{2.303RT}{F}$ = 0.06 V)

Answer 1

The correct answer is 7
$Q = \frac{[H^+]^2 }{[ Cu^{+2} ] pH_2} = \frac{10^{-6}}{C} pH_2 = 1$

$E = E^º_{cell} - \frac{0.06}{n} log Q$

$0.31 = 0.34 - \frac{0.06}{2} log \frac{10^{-6}}{C}$

$log \frac{10^{-6}}{C} = 1$
C = 10-7 M
x = 7