Question

The $pH$ of an aqueous solution of a $0.1M$ solution of a weak monoprotic acid which is $1$% ionised is:

• A. $1$
• B. $2$
• C. $3$
• D. $11$

Answer 1

Answer: (C)

$3$

Concentration of solution $=C=0.1M$

Dissociation is $\alpha =0.01$

After dissociation, the concentration of $H^{+}$ ions will be $C\alpha =0.1\times 0.01={10}^{-3}=\left[H^{+}\right]$

We know the fomrula for pH as

$pH=-log\left[H^{+}\right]=-log\left({10}^{-3}\right)=+3$