Question

At what pH of HCl solution will hydrogen gas electrode show electrode potential of $-0.118V$ $H_2$ gas is bubbled at 298 K and 1 atm pressure?

• A. 2
• B. 4
• C. 6
• D. 8

Answer 1

Answer: (A)

2

$H^{+}+e^{-}\to \frac{1}{2}{H}_2$

On applying Nernst equation:

$E_{H^{+}/H_2}=E_{H^{+}/H_2}^0-\frac{0.0591}{1}log\frac{1}{H^{+}}$

$-0.118=0-\frac{0.0591}{1}log\frac{1}{H^{+}}$

$-0.118=-0.0591\times \left(log\frac{1}{H^{+}}\right)$

$-0.118=-0.0591\times (-log{H}^{+})$

$-0.118=-0.0591\times pH$

$pH=2$

Hence, the correct answer is option $\text{A}$.