Question

The normality of 0.3 M phosphorous acid $\left(H_{3}P{O}_3\right)$ is
(IIT-JEE, 1999)

• A. 0.1
• B. 0.9
• C. 0.3
• D. 0.6

Answer 1

The correct option is D 0.6

$HO-\stackrel{\stackrel{O}{|}|}{\underset{\underset{H\left(H_{3}P{O}_3\right)}{|}}{P}}-OH$
Only hydrogens attached to oxygen and contribute to basicity are replaceable. From the structures it is clear that phosphorus acid, $H_{3}P{O}_3,$ is dibasic.
Normality = Molarity $\times$ Basicity (for an acid)
N = 0.3 $\times$ 2 = 0.6