Question

The pH of an aqueous solution of $CH_3COONa$ of concentrated $C(M)$ is given by

• A. $7-\frac{1}{2}pK_{a}-\frac{1}{2}log\,C$
• B. $\frac{1}{2}pK_{w}+\frac{1}{2}pK_{b}+\frac{1}{2}log\,C$
• C. $\frac{1}{2}pK_{w}-\frac{1}{2}pK_{b}-\frac{1}{2}log\,C$
• D. $\frac{1}{2}pK_{w}+\frac{1}{2}pK_{a}+\frac{1}{2}log\,C$

Answer 1

Answer: (D)

$CH _{3} COONa + H _{2} O \rightleftharpoons \underset{\text { Weak acid }}{ CH _{3} COOH } + \underset{\text{Strong base}}{NaOH}$
As sodium acetate is a salt of weak acid and strong base, in hydrolysis of sodium acetate the $pH$ is given by
$pH =\frac{1}{2} p K_{w}+\frac{1}{2} p K_{a}+\frac{1}{2} \log C$