Q. For a weak acid $pK_{a}$ is 4.8. What will be the ratio of concentration of acid and salt in pH 5.8 solution?
A) 10
B) 3
C) 9
D) 0.1
Explanation
(d)
$\because$ $pH = pK_{a} + \log\frac{\lbrack salt\rbrack}{\lbrack acid\rbrack}$
or $5.8 = 4.8 + \log\frac{\lbrack salt\rbrack}{\lbrack acid\rbrack}$
or $\log\frac{\lbrack salt\rbrack}{\lbrack acid\rbrack} = 1.0$
$\frac{\lbrack salt\rbrack}{\lbrack acid\rbrack} = anti - \log{1.0 = 10}$
$\therefore$ $\frac{\lbrack acid\rbrack}{\lbrack salt\rbrack} = \frac{1}{10} = 0.1$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.