A buffer solution prepared from $\mathrm{CH}_{3} \mathrm{COOK}$ and $\mathrm{CH}_{3} \mathrm{COOH}$

Question

A buffer solution prepared from $\mathrm{CH}_{3} \mathrm{COOK}$ and $\mathrm{CH}_{3} \mathrm{COOH}$ has $\mathrm{pH}=5.24$. ( pKa for acetic acid is 4.74). The ratio of $\frac{\left[\mathrm{CH}_{3} \mathrm{COO}^{-}ight]}{\left[\mathrm{CH}_{3} \mathrm{COOH}ight]}$ in this buffer solution is\

Professor PC Thomas Classes · Answer

Henderson equation for an acidic buffer is\ $\mathrm{pH}=\mathrm{pKa}+\log \frac{[\mathrm{salt}]}{[	ext { acid }]} 5.22=4.74+\log \frac{[\mathrm{salt}]}{[	ext { acid }]}$\ $	herefore \log \frac{[\mathrm{salt}]}{[\mathrm{acid}]}=5.22-4.74=0.48$\ $\frac{[	ext { salt }]}{[	ext { acid }]}=$ antilog of $0.48 \approx 3$. ie., $3: 1$