In which of the following is the oxidation number of sulphur equal to -2?
Answer Details
S8, H2S, SO2, and SO32- are all compounds that contain sulfur, but the oxidation number of sulfur is only -2 in one of them. The oxidation number of an atom is a measure of the number of electrons that it has gained or lost in a chemical reaction. In S8, the oxidation number of sulfur is zero because it is in its elemental state and has not gained or lost any electrons. In H2S, the oxidation number of sulfur is -2 because hydrogen has an oxidation number of +1 and the overall charge of the compound is 0. In SO2, the oxidation number of sulfur is +4 because oxygen has an oxidation number of -2 and the overall charge of the compound is 0. In SO32-, the oxidation number of sulfur is +4 because oxygen has an oxidation number of -2 and the overall charge of the ion is -2. Therefore, the only compound in which the oxidation number of sulfur is -2 is H2S.