Question

What will be the oxidation potential for the following hydrogen half cell at $1$ atm pressure and ${25}^{o}C$ temperature?

$Pt\left|H_{2\left(g\right)}\right|HCl\left(aq\right)$ when $pH=3$ and pressure of $H_2$ gas is 1 bar.

• A. $0.059V$
• B. $0.188V$
• C. $0.177V$
• D. $0.000V$

Answer 1

Answer: (C)

$0.177V$

The reduction reaction is $2H^{+}+2e^{-}\to H_2$

Pressure $P=1$ bar $=0.9869$ atm

$pH=3$

$\left[H^{+}\right]={10}^{-pH}={10}^{-3}M$

$E_{SHE}^o=0.0V$

$E_{HE}=E_{SHE}^o-\frac{0.0591}{n}lo{g}_{10}\frac{P_{H_2}}{[H^{+}{]}^2}$

$E_{HE}=0.0V-\frac{0.0591}{2}lo{g}_{10}\frac{0.9869}{[{10}^{-3}{]}^2}$

$E_{HE}=-0.177V$

This is the reduction potential. The oxidation potential is $+0.177V$