Q12 / 50 · Manipal (MET) 2023 · Chemistry
The $\mathrm{pK}_a$ of acetic acid is 4.74. The concentration of $\mathrm{CH}_3 \mathrm{COOH}$ is 0.01 M . The pH of $\mathrm{CH}_3 \mathrm{COOH}$ is____
Correct answer: 3.37
Solution
For a weak acid,
$\mathrm{pH}=\frac{1}{2}\left[\mathrm{p} K_{\mathrm{a}}-\log C\right]$
$\begin{aligned} & =\frac{1}{3}\left[4.74-\log 10^{-2}\right] \\ & =\frac{1}{2} \times 6.74=3.37\end{aligned}$
Hence, the correct answer is 3.37.