In the reaction represented by the equation; 2FeCI3 + SO2 + 2H2O → 2FeCL2 + H2SO4 + 2HCI the oxidation number of sulphur changes from

In the given chemical reaction, the oxidation number of sulfur changes from 4 in SO₂ to 6 in H₂SO₄. Oxidation number is the charge an atom would have if the shared electrons were assigned to the more electronegative atom in a compound. In SO₂, oxygen has an oxidation number of -2, and since there are two oxygen atoms, the total charge from oxygen is -4. Therefore, to balance the charge of SO₂, sulfur has an oxidation number of +4. In H₂SO₄, oxygen still has an oxidation number of -2, and since there are four oxygen atoms, the total charge from oxygen is -8. Hydrogen has an oxidation number of +1, and there are two hydrogen atoms, for a total charge of +2. To balance the charge of H₂SO₄, sulfur must have an oxidation number of +6. Therefore, the oxidation number of sulfur changes from +4 to +6 in this reaction.