In which of the following is the oxidation number of sulphur equal to -2?
Answer Details
The oxidation number of sulfur (S) is the hypothetical charge that an atom would have if all its bonds to atoms of different elements were completely ionic in nature. To determine the oxidation number of sulfur in each compound given, we need to follow some rules:
- The oxidation number of an atom in its free (uncombined) state is zero.
- The oxidation number of a monatomic ion is equal to its charge.
- The sum of the oxidation numbers of all atoms in a neutral molecule must be zero.
- The sum of the oxidation numbers of all atoms in a polyatomic ion must equal the charge on the ion.
Using these rules, we can find the oxidation number of sulfur in each compound:
- In S8, sulfur is in its elemental form, and the oxidation number of each atom is zero.
- In H2S, hydrogen (H) has an oxidation number of +1, and the sum of the oxidation numbers in the molecule is zero. Therefore, sulfur must have an oxidation number of -2 to balance out the charge.
- In SO2, oxygen (O) has an oxidation number of -2, and the sum of the oxidation numbers in the molecule is zero. Therefore, sulfur must have an oxidation number of +4 to balance out the charge.
- In SO32-, oxygen has an oxidation number of -2, and the sum of the oxidation numbers in the ion is -2. Therefore, sulfur must have an oxidation number of +4 to balance out the charge.
Therefore, the compound in which the oxidation number of sulfur is equal to -2 is H2S.