Question

What is the oxidation number of phosphorus in phosphoric acid ( $H_{3}P{O}_4$)?

• A. +5
• B. +3
• C. -3
• D. -5

Answer 1

The correct option is A

+5

The chemical formula for the compound given to us is $H_{3}P{O}_4$.

Let the oxidation number of phosphorus be $x$.

We know the oxidation numbers for hydrogen and oxygen are +1 and -2 respectively.

Since the compound given to us has no overall charge, therefore, the total oxidation number for this compound is taken equal to zero. So the sum of the values of the oxidation states in this compound will also be equal to zero. So we get an equation like this.

$3\times (+1)+x+[4\times (-2\left)\right]=0$

$3+x-8=0$

$x-5=0$

$x=+5$

Hence the oxidation number of Phosphorus(P) in Phosphoric acid($H_{3}P{O}_4$) is equal to +5.