The oxidation number of sulphur in sulphuric acid, H2SO4, is
- A. plus 2
- B. plus 6
- C. minus 2
- D. plus 4
Explanation
Hydrogen contributes plus 1 each and oxygen minus 2 each, so 2 plus x minus 8 equals zero and x is plus 6. The value plus 4 belongs to sulphur in sulphur dioxide and in sulphurous acid, which is why it is the closest distractor. Sulphur at plus 6 is already at its maximum oxidation state, so concentrated sulphuric acid can act as an oxidising agent but not as a reducing one.