Question

By how much times will potential of half cell $C{u}^{+2}/Cu$ change if the solution is diluted to 100 times at 298 K?

• A. Increases by 59 mV
• B. Decrease by 59 mV
• C. Increases by 29.5 mV
• D. Decrease by 29.5 mV

Answer 1

The correct option is B Decrease by 59 mV

For the fraction $C{u}^{+2}+2e^{-}\to Cu$

Nernst equation is

$E=E^0-\frac{RT}{2F}ln\frac{1}{\left[C{u}^{+2}\right]}$

After diluting the solution 100 times we have

$E_2-E_1=-\frac{RT}{2F}ln\frac{\left[C{u}^{+2}\right]}{0.01\left[C{u}^{+2}\right]}$

$\frac{RT}{2F}ln\left(0.01\right)=\frac{-2\times 0.059}{2}$

$=-0.059V$

Potential of half cell will decrease by 59 mV.