Chemistry - Redox Reactions Question with Solution | TestHub

Phosphorus acid ${\mathrm{H}}_3\mathrm{P}{\mathrm{O}}_3$: 3(+1) + $x$ + 3(-2) = 0 $\Rightarrow$ $x$ = +3. Metaphosphoric ($\mathrm{HP}{\mathrm{O}}_3$), pyrophosphoric (${\mathrm{H}}_4{\mathrm{P}}_2{\mathrm{O}}_7$) and orthophosphoric (${\mathrm{H}}_3\mathrm{P}{\mathrm{O}}_4$) acids all have P = +5. Hence (c).