Question

The standard electrode potential of $Cu|C{u}^{+2}$ is $-0.34$ Volt. At what concentration of $C{u}^{+2}$ ions, electrode potential will be zero?

• A. $1.98\times {10}^{-12}M$
• B. $2.98\times {10}^{-12}M$
• C. $1.49\times {10}^{-12}M$
• D. $5.96\times {10}^{-12}M$

Answer 1

The correct option is B $2.98\times {10}^{-12}M$

Solution:- (B) $2.98\times {10}^{-12}M$

Given that:-

${E^0}_{cell}=-0.34V$

$E_{cell}=0$

$\left[{Cu}^{2+}\right]=?$

The emf of electrode when dipped in different cocentrated solution is given by Nernst equation.

$E_{cell}={E^0}_{cell}+\frac{0.059}{2}\log \left[{Cu}^{2+}\right]$

$\Rightarrow 0=0.34+\frac{0.059}{2}\log \left[{Cu}^{2+}\right]$

$\Rightarrow \log \left[{Cu}^{2+}\right]=-0.34\times 0.0295$

$\Rightarrow \log \left[{Cu}^{2+}\right]=-11.52$

$\Rightarrow \left[{Cu}^{2+}\right]\approx 2.98\times {10}^{-12}M$