Question

A buffer solution has equal volumes of $0.2M \, NH_4OH$ and $0.02\, M \, NH_4 Cl$. The $p^{kb}$ of the base is $5$. The $pH$ is

• A. 10
• B. 9
• C. 4
• D. 7

Answer 1

Answer: (A)

10

Answer 2

$pOH = p K_{b}+\log \frac{[ salt ]}{[ base ]}$

(Henderson's equation)

$=5+\log \frac{0.02}{0.2}=5+\log \frac{1}{10}$
$=5+(-1)=4$
$pH =14- pOH =14-4=10$