Question

The basicity of phosphorus acid is the same as the basicity of:

• A. $H{NO}_3$
• B. $H_2{SO}_4$
• C. $H_3{PO}_4$
• D. $HCl$

Answer 1

Answer: (B)

$H_2{SO}_4$

Phosphorus acid is a dibasic acid as it contains two acidic protons. $H_{3}P{O}_3$ is more clearly described with the structural formula ${HPO\left(OH\right)}_2$. That is similar to sulphuric acid $H_{2}S{O}_4$ which is a dibasic acid and can donate two hydrogens.
${HPO\left(OH\right)}_2+2H_{2}O\to HP{O}_3^{2-}+2H_3{O}^{+}$
$H_{2}S{O}_4+2H_{2}O\to S{O}_4^{2-}+2H_3{O}^{+}$