Final answer:
Sulfur-containing materials typically form hydrogen sulfide gas (H₂S) when treated with a reducing agent. In the presence of hot, concentrated sulfuric acid, sulfur dioxide (SO₂) is commonly formed, especially in the absence of water. Option number d is correct.
Step-by-step explanation:
When sulfur-containing materials are treated with a reducing agent, they typically form hydrogen sulfide gas (H₂S). In the presence of hot, concentrated sulfuric acid, many reducing agents, including hydrogen sulfide itself, can lead to the formation of a variety of reduced sulfur compounds.
However, the sulfur in these materials, including hydrogen sulfide, is often oxidized to elemental sulfur or to various oxidized sulfur species such as sulfate (SO₄²⁻) or sulfite (SO₃²⁻), depending on the specific conditions and the presence of water. A common result of hot sulfuric acid treatment, especially in the absence of water, can be the formation of sulfur dioxide (SO₂), which is a gas at room temperature and often produced when sulfide minerals are roasted in air or when sulfuric acid reacts with sulfite salts.