Question

Calculate the oxidation number of phosphorus in the following species.

A) $HP{O}_3^2-$

B) $P{O}_4^3-$

Answer 1

A)
Let the oxidation number of phosphorous be $x$ in $HP{O}_3^{2-}$
$+1+x+(-2)\times 3=-2$
$+1+x-6=-2$
$x–5=-2$
$x=+3$
Hence, oxidation number of phosphorus in $HP{O}_3^2-$ is $+3$.

B)
Let the oxidation number of phosphorous be $x$ in $P{O}_4^{3-}$
$x+(-2)\times 4=-3$
$x–8=-3$
$x=+5$

Thus, oxidation number of phosphorus in $P{O}_4^{3-}$ is $+5$.