Question

The oxidation potential of hydrogen electrode $H_2/H_3{O}^{+}\left(aq\right)$ will be greater than zero of :

• A. concentratio of $H_3{O}^{+}$ ions is 1M
• B. concentratio of $H_3{O}^{+}$ ions is 2M
• C. partial pressure of $H_2$ gas is 2 atm
• D. E(oxidation) can never be +ve

Answer 1

The correct option is C partial pressure of $H_2$ gas is 2 atm

The Nernst equation for $E_{H_2}$ for reduction is $E_{H_2}=E_0^{H_2}-\frac{0.0592}{n}log\frac{P_{H_2}}{{\lfloor H^{+}\rfloor }^2}$, but $E_0^{H_2}=0$. When partial pressure of hydrogen gas is 2 atm, the term $log\frac{P_{H_2}}{{\lfloor H^{+}\rfloor }^2}$ is positive. Hence the reduction potential will be negative and the oxidation potential will be positive.