The reduction potential (in volt) of a hydrogen electrode set up with a $2 imes 10^{-2} \mathrm{M}$ aqueous solution of a weak mono basic acid $\left(\mathrm{K}_{\mathrm{a}}=5 imes 10^{-5}ight)$ at one atmosphere and $25^{\circ} \mathrm{C}$ is

Question

The reduction potential (in volt) of a hydrogen electrode set up with a $2 	imes 10^{-2} \mathrm{M}$ aqueous solution of a weak mono basic acid $\left(\mathrm{K}_{\mathrm{a}}=5 	imes 10^{-5}ight)$ at one atmosphere and $25^{\circ} \mathrm{C}$ is

Aicharya · Accepted Answer

$\begin{aligned} H A & ightarrow H^{+}+A^{-} \ K a & =\frac{\left[H^{+}ight]\left[A^{-}ight]}{[1+A]} \ {\left[H^{+}ight] } & =\left[A^{-}ight]=x \ 5 \times 10^{-5} & =\frac{x^2}{2 \times 10^{-2}} \ x^2 & =10^{-6} \ x & =10^{-3} \ E & =E^0-\frac{0.0591}{n} \log \frac{1}{\left[H^{+}ight]} \ & =0-0.0591 \log \frac{1}{10^{-3}} \ & =-0.0591 \times 3 \ & =-0.1773 \end{aligned}$

The reduction potential (in volt) of a hydrogen electrode set up with a $2 \times 10^{-2} \mathrm{M}$…

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