The oxidation number of sulphur in sulphuric acid, H2SO4, is
Correct answer: B. plus 6
- 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.
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About Oxidation and Reduction
Oxidation involves loss of electrons, increase in oxidation number or addition of oxygen, while reduction involves electron gain, decrease in oxidation number or removal of oxygen. The topic covers oxidising and reducing agents, oxidation-number changes, redox equations and the distinction between oxidation at the anode and reduction at the cathode.
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