Question

$H_{2}X$ is a dibasic acid which dissociates completely in water. Which one of the following is the molarity of an aqueous solution of this acid which has a $pH$ of $1$?

• A. $0.1$
• B. $0.05$
• C. $0.2$
• D. $0.5$

Answer 1

The correct option is B $0.05$

$pH$ of a medium is the negative of the log of the concentration of $H^{+}$ ions present in it.

$pH=-log\left[H^{+}\right]=1$

$\left[H^{+}\right]=0.1M$

Now,

$H_{2}X⟶2H^{+}+X^{2-}$

$M_{H_{2}X}=\frac{0.1}{2}=0.05M$

Hence molarity is 0.05M.