Question

Which of the following statement (s) is (are) correct?

• A. The pH of $1.0\times 10^{-8}M$ solution of $HCl$ is $8$
• B. The conjugate base of $H_{2}P{O}_4^{-}$ is $HP{O}_4^{3-}$
• C. Autoprotolysis constant of water increases with temperature
• D. When a solution of a weak monoprotic acid is titrated against a strong base, at half-neutralisation point $pH=\left(\frac{1}{2}\right)p{K}_a$

Answer 1

Answer: (B), (C)

$pH$ of $10^{8}M$ solution will be between $6$ and $7$ but never $8.$ The conjugate base of an acid is formed by removing a proton $\left(H^{+}\right)$from acid. Therefore, $HP{O}_4^{2-}$ is a conjugate base of $H_{2}P{O}_4^{-}$
$H_{2}O\rightleftharpoons H^{-}+OH$
$△H>0$
Increasing temperature will increase equilibrium constant of the above endothermic reaction.
At the mid-point of titration $pH=p{K}_a$.