Question

Which is not true about $H_{3}P{O}_2$?

• A. It is tribasic acid
• B. One mol is neutralised by 0.5 mol $Ca(OH{)}_2$
• C. $Na{H}_{2}P{O}_2$ is normal salt
• D. It disproportionates to $H_{3}P{O}_3$ and $P{H}_3$ on heating

Answer 1

The correct option is A It is tribasic acid

$H_{3}P{O}_2$ is monobasic acid.
Its dissociation reaction is $H_{3}P{O}_2\rightleftharpoons H^{+}+{H_{2}P{O}_2}^{-}$
Two moles of $H_{3}P{O}_2$ reacts with one mole of $Ca(OH{)}_2$
$2H_{3}P{O}_2+Ca(OH{)}_2\to Ca(H_{2}P{O}_2{)}_2+2H_{2}O$
On heating, it disproprotionates to
$2H_{3}P{O}_2\to H_{3}P{O}_3+P{H}_3+\frac{1}{2}{O}_2$