Question

Dissociation constants of $CH_3COOH$ and $NH_4OH$ in aqueous solution are $10^{-5}$. If $pH$ of a $CH_3COOH$ solution is $3$, What will be the $pH$ of $NH_4OH$?

• A. $3.0$
• B. $4.0$
• C. $10.0$
• D. $11.0$

Answer 1

Answer: (D)

$11.0$

Answer 2

$pH$ of $CH_3COOH = 3$ $\left[H^{+}\right]=10^{-3}\,M$ from $CH_{3}COOH$ $\left[NH_{4}OH\right]=\left[CH_{3}COOH\right]=10^{-3}\,M$ $\left[OH^{-}\right]=10^{-3}\,M$ $\left[H^{+}\right]\left[OH^{-}\right]=10^{-14}$ $\left[H^{+}\right]=\frac{10^{-14}}{10^{-3}}=10^{-11}$ $pH$ of $NH_{4}OH=-log\,\left(10^{-11}\right)$ $=11$