Question

Consider the single electrode process $4H^{+} + 4^{-} e 2H _2$ catalyzed by platinum black electrode in $HCl$ electrolyte. The potential of the electrode is $-0.059\,V$ $V. SHE$. What is the concentration of the acid in the hydrogen half cell if the $H_2$ pressure is $1$ bar ?

• A. 1 M
• B. 10 M
• C. 0.1 M
• D. 0.01 M

Answer 1

Answer: (C)

0.1 M

Answer 2

$4 H ^{+}+4 e^{-} {<=>}2 H _{2}$
$E=E^{\circ}-\frac{0.059}{n} \log \frac{p H_{2}}{\left[ H ^{+}\right]^{4}}$
$-0.059=0-\frac{0.059}{4} \log \frac{1}{\left[ H ^{+}\right]^{4}}$
$=\left[ H ^{+}\right]=10^{-1}=0.1 M$