Chemistry - Ionic Equilibrium Question with Solution | TestHub

The given solution is an acidic buffer solution.

According to the Henderson equation for acidic buffer,

$\mathrm{pH}={\mathrm{pK}}_{\mathrm{a}}+{\log }_{10}\frac{\left[\mathrm{salt}\right]}{\left[\mathrm{acid}\right]}$

Given that, 

$$\begin{gathered} {\mathrm{pK}}_{\mathrm{a}}=4.57 \\ \left[\mathrm{salt}\right]=\left[\mathrm{sodium} \mathrm{acetate}\right]=0.1\mathrm{M} \\ \left[\mathrm{Acid}\right]=\left[\mathrm{Acetic} \mathrm{acid}\right]=0.01\mathrm{M} \end{gathered}$$

Hence, the

$\mathrm{pH}=4.57+\log \frac{0.1}{0.01}=4.57+1=5.57$