Question

Three reactions involving $H_{2}P{O}_4^{-}$ are given below:

(i) $H_{3}P{O}_4+H_{2}O\to H_3{O}^{+}+H_{2}P{O}_4^{-}$
(ii) $H_{2}P{O}_4^{-}+H_{2}O\to HP{O}_4^{2-}+H_3{O}^{+}$
(iii) $H_{2}P{O}_4^{-}+O{H}^{-}\to H_{3}P{O}_4+O^{2-}$

In which of the above reactions, does $H_{2}P{O}_4^{-}$ act as an acid?

• A. (ii) only
• B. (i) and (ii)
• C. (iii) only
• D. (i) and (iii)

Answer 1

Answer: (A)

(ii) only

An acid is one which can accept a pair of $e^{-}$ or donate $H^{+}$. In $\left(ii\right)$ only $H_{2}P{O}_4^{-}$ acts as an acid by donating $H^{+}$ to water.