Question

Assign oxidation number to the underlined element in $Na{H}_2\underset{–}{P}{O}_4$.

Answer 1

Let X be the oxidation state of P in $Na{H}_{2}P{O}_4$.

We know that oxidation no. for $O=-2,H=+1,Na=+1,$
$+1+2(+1)+X+4(-2)=0\Rightarrow X=+5$
Hence, the oxidation state of P in $Na{H}_{2}P{O}_4$ is +5.