Question

Which salt can furnish $H^{+}$ in its aqueous solution?

• A. $Na{H}_{2}P{O}_2$
• B. $N{a}_{2}HP{O}_3$
• C. $N{a}_{2}HP{O}_4$
• D. all of these

Answer 1

Answer: (B)

$N{a}_{2}HP{O}_3$

• Disodium hydrogenphosphite$\left(N{a}_{2}HP{O}_3\right)$ is a salt of phosphorus acid $\left(H_{3}P{O}_3\right)$, which is a dibasic acid. A dibasic acid has only two acidic or replaceable hydrogen atoms in its molecule. In $\left(H_{3}P{O}_3\right)$, the third hydrogen is directly bonded to phosphorus and so it is non-acidic.
  
• $N{a}_{2}HP{O}_3$ is formed when the two acidic hydrogens are replaced by sodium. In other words, this salt is the product of complete neutralisation of phosphoric acid by sodium hydroxide. It does not have any acidic hydrogen. So, it can furnish any $H^{+}$ in its aqueous solution.