Chemistry - Complete P-block Question with Solution | TestHub

The reaction is:

$$P_4+3NaOH+3H_{2}O\to P{H}_3(X)+3Na{H}_{2}P{O}_2(Y)$$

X is phosphine ($P{H}_3$), Y is sodium hypophosphite ($Na{H}_{2}P{O}_2$).

Reaction of Y with acid:

$$Na{H}_{2}P{O}_2+HCl\to H_{3}P{O}_2(Z)+NaCl$$

Z is hypophosphorous acid ($H_{3}P{O}_2$).

A) $P{H}_3$ is a weak base, reacting with $HI$ to form $P{H}_{4}I$. (Correct)

B) In $Na{H}_{2}P{O}_2$, the oxidation state of P is $+1$. ($1+2(1)+x+2(-2)=0\Rightarrow x=+1$). (Correct)

C) $H_{3}P{O}_2$ has one P-OH bond and two P-H bonds. Only the H attached to O is acidic, making it a monoprotic acid. (Incorrect)

D) The bond angle in $P{H}_3$ (approx. $93.5^{\circ }$) is less than in $N{H}_3$ (approx. $107^{\circ }$) due to P's larger size and lower electronegativity. (Correct)

The INCORRECT statement is C.