Chemistry - Complete P-block Question with Solution | TestHub

Identification: Non-metal $X$ is White Phosphorus ($P_4$), its most reactive allotrope, which reacts with $NaOH(aq)$ to produce $Na{H}_{2}P{O}_2(Salt(aq))$ and $P{H}_3(Y(g))$.

Acid Formation: Reacting the salt with $H^{+}$ forms hypophosphorous acid, $Z=H_{3}P{O}_2$.

Heating Effect: Heating $Z$ causes disproportionation into phosphoric acid, $Q=H_{3}P{O}_4$ (an 'ic' acid where $P$ is $+5$), and $P{H}_3(Y(g))$.

Oxidation States: The oxidation states of the central phosphorus atom are $0$ in $X(P_4)$, $+1$ in $Salt$ and $Z$, and $-3$ in $Y(P{H}_3)$.

Conclusion: The compound with the lowest oxidation state ($-3$) is $Y$.