If the pressure of H2 gas is increased from 1 atm to 100 atm keeping H+ concentration constant at 1 M, the change in reduction potential of hydrogen half-cell at 25°C will be
Answer & explanation
Correct answer: option 1
The half-cell reaction for hydrogen half-cell acting as cathode is
\(2H^+ + 2e^- \rightarrow H_2\)
\(E_{H^+|H_2} = E^0_{H^+|H_2} − \frac{0.059}{2}log\frac{p_{H_2}}{[H^+]^2}\)
Now, when the pressure of of \(H_2\) gas is changed to 100atm without changing \([H^+]\), the reduction potential becomes
\(E^´_{H^+|H_2} = − \frac{0.0591}{2}log\frac{100}{[H^+]^2}\)
∴ Change in reduction potential =
\(E_{H^+|H_2} − E^´_{H^+|H_2} = \frac{0.0591}{2}log\frac{100}{[H^+]^2} × \frac{[H^+]^2}{1}= 0.059 V\)