Question

Among the hydrides given below which are reasonably good acid?

• A. $HF$
• B. $N{H}_3$
• C. $NaH$
• D. $H{N}_3$

Answer 1

Answer: (A)

The $p{K}_a$ values of the given compounds are:
$H{N}_3$:4.6
$HF$:3.17
$N{H}_3$:38
$NaH$:35
Higher the $p{K}_a$ lower will be the acidic strength. Since the $p{K}_a$ of $N{H}_3$ and $NaH$ are too high, they are basic in nature. Therefore among the given compounds $HF$ and $H{N}_3$ are acidic and $HF$ is more acidic.
Option B is correct.