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Hydrogen sulfide behaves only as a reducing agent, whereas sulfur dioxide can function as both a reducing agent and an oxidizing agent, because

1. oxygen is more electronegative in SO2
2. hydrogen in H2S has a more positive character than oxygen
3. sulfur in SO2 shows only one oxidation state
4. sulfur in H2S has an oxidation state of −2

Correct answer: sulfur in H2S has an oxidation state of −2

Solution

H2S can only reduce because sulfur is in its lowest oxidation state (-2) and can only be oxidised; SO2 (S at +4, intermediate) can do both. The correct reason is option 3, not the hydrogen-character statement.

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