Question

For the cell $Pt\left|H_2(g)\right|$ solution $X\Vert KCl$ (saturated) $\left|H{g}_{2}C{l}_2\right|Hg\mid Pt$, the observed $EMF$ at $25^{\circ }C$ was $600mV$. When solution $X$ was replaced by a standard phosphate buffer with $pH=7.00$, the $EMF$ was $718mV$. Find the $pH$ of solution $X$.

Answer 1

Answer: 5

subtracting we get
$0.118=0.059\log \frac{\left[H^{+}\right]}{10^{-7}}$
$\Rightarrow \frac{\left[H^{+}\right]}{10^{-7}}=100$
$\Rightarrow \left[H^{+}\right]=10^{-5}$
$\Rightarrow pH=5$