Question

What is the oxidation state of S in the following compound?

H₂SO₃

Answer 1

Let the oxidation state of sulphur be x.

Now write the formula again:

H₂SO₃

Hydrogen (H) = +1, and there are 2 H atoms → 2 × (+1) = +2

Oxygen (O) = –2, and there are 3 O atoms → 3 × (–2) = –6

The overall molecule is neutral, so the total oxidation states must sum to 0.

2(+1) + x + 3(–2) = 0

2 + x − 6 = 0

x − 4 = 0

x = +4

∴ The oxidation state of S in H₂SO₃ is +4.