Question

The standard reduction potential values, $E^{\circ }\left(B{i}^{3+}/Bi\right)$ and $E^{\circ }\left(C{u}^{2+}/Cu\right)$ are 0.226 V and 0.344 V respectively. A mixture of salts of bismuth and copper at unit concentration each is electrolysed at ${25}^{\circ }C$. To what value can $\left[C{u}^{2+}\right]$ be brought down before bismuth starts to deposit, in electrolysis.

• A. $\left[C{u}^{2+}\right]={10}^{-8}M$
• B. $\left[C{u}^{2+}\right]={10}^{-4}M$
• C. $\left[C{u}^{2+}\right]={10}^{-3}M$
• D. $\left[C{u}^{2+}\right]={10}^{-6}M$

Answer 1

The correct option is B $\left[C{u}^{2+}\right]={10}^{-4}M$

The concentration of $C{u}^{2+}$ ions should be brought down to ${10}^{-4}M$ before bismuth starts to deposit.