Question

Which of the following is correct for indentification of the polyacidic bases and polybasic acids respectively?

• A. $H_{3}P{O}_4$ and $B(OH{)}_3$
• B. $Mg(OH{)}_2$ and $B(OH{)}_3$
• C. $Mg(OH{)}_2$ and $H_{2}S{O}_4$
• D. $NaOH$ and $H_{3}P{O}_4$

Answer 1

The correct option is C $Mg(OH{)}_2$ and $H_{2}S{O}_4$

• Polybasic acids are those when dissolved in water they ionize and give rise to more than one proton.
• Polyacidic bases are those which release more than one $O{H}^{-}$ ions per molecule of base in aqueous solution.

1. $H_{3}P{O}_4$ is a polybasic acid, as it has more than ionizable $H^{+}$ ions and $B(OH{)}_3$ is actually a weak acid which reacts with $H_{2}O$ and gives one $H^{+}andB(OH{)}_4^{-}$ ion. So, it is incorrect.
2. $Mg(OH{)}_2$ is a poly acidic base as it has more than one ionizable$O{H}^{-}$ ions. But $B(OH{)}_3$ acts as a weak monobasic acid.So , it is incorrect.
3. $Mg(OH{)}_2$ is a polyacidic base and $H_{2}S{O}_4$ is polybasic acid as it has more than one ionizable protons. So, it is correct.
4. $NaOH$ is a not polyacidic base as it has only one replacable hydroxyl ion and $H_{3}P{O}_4$ is polybasic acid as it has three ionizable protons. So, it is correct.