Question

What is the reduction potential of hydrogen gas electrode when pure hydrogen gas is at 1 atmosphere pressure and platinum electrode is in contact with HCI of pH 2 at 298 K?

Options

• − 0.0296 V

• − 0.0592 V

• − 0.1184 V

• − 0.1592 V

Answer 1

− 0.1184 V

Explanation:

\[2\mathrm{H}_{(\mathrm{aq})}^++2\mathrm{e}^-\longrightarrow\mathrm{H}_{2(\mathrm{g})}\]

∴ \[\mathrm{n=2,~E_{H_{2}}^{o}=0}\] and p_H2 = 1atm

Given pH = 2, i.e., [H⁺] = 10^-2 M

∴ Reduction potential of hydrogen gas electrode

\[\mathrm{E_{H_{2}}=~E_{H_{2}}^{o}-~\frac{0.0592}{n}\log_{10}\frac{P_{H_{2}}}{\left[H^{+}\right]^{2}}}\]

\[=0-\frac{0.0592}{2}\log_{10}\frac{1}{\left(10^{-2}\right)^{2}}\]

\[=-\frac{0.0592}{2}\log_{10}10^4\]

\[=-\frac{4\times0.0592}{2}=-0.1184\mathrm{V}\]