The oxidation state of phosphorus is + 3 in

a) Orthophosphoric acid b) Phosphorus acid

c) Metaphosphoric acid d) Phyrophosphoric acid

b) Phosphorus acid

Explanation:

To distinguish the type of acid of phosphorus with the oxidation state of + 3, we need to be familiar with the chemical formula of each of the compounds:

Orthophosphoric acid H₃PO₄

Phosphorus acid H₃PO₃

Metaphosphoric acid HPO₃

Phyrophosphoric acid H₄P₂O₇

Now that we know the formula of the given compounds, the algebraic sum of all the oxidation numbers of all atoms in a neutral compound is zero:

Only phosphorus acid yielded an oxidation state of + 3 for phosphorus in the compound.

H₃PO₃:

we know the oxidation state of H = + 1

O = - 2

The oxidation state of P is unknown. We can express this as an equation:

3 (+1) + P + 3 (-2) = 0

3 + P - 6 = 0

P-3 = 0

P = + 3