Question

$20 \, ml$ of $0.1 \, M \, NaOH$ is added to $30 \text{ ml} 0.1 \text{ M NaOH } 30 \text{ ml} \, 0.2 \left(\text{ M CH}\right)_{3} \text{COOH } \left(\left(\text{pK}\right)_{\text{a}} = 4.74\right)$ , calculate the $\text{pH}$ of the resulting solution? [given: $log 2=0.3$ ]

• A. 3.44
• B. 4.01
• C. 4.44
• D. 4.71

Answer 1

Answer: (C)

The resulting solution is an acidic buffer. so $\text{pH} = \text{pK}_{\text{a}} + log \frac{\left[\text{Salt}\right]}{\left[\text{Acid}\right]}$

$=4.71+log \frac{2}{4}$

$=4.44$