Question

The $pKa$ of a weak acid is $4.8$. What should be the ratio of [acid]/[salt], if a buffer of $pH=5.8$ is required?

• A. 0.1
• B. 10
• C. 1
• D. 2

Answer 1

Answer: (A)

Given = The expression for the pH of the aridic buffer solution is vas given
$pH=p{k}_a+\log \frac{[\text{ salt }]}{[\text{ Acid }]}$
$p{K}_a=4.8$
Substitute value in the above equation
$5\cdot 8=4\cdot 8+\log [\frac{\text{ Salt }]}{\text{ [Arid] }}$
Hence, $\frac{\text{ [salt] }}{\text{ [Acid]}}=\frac{10}{1}=10:1$
$i,e=0.1$