What happens when zinc sulphide undergoes roasting? 

Zinc oxide is formed 

The correct answer is option 3. Zinc oxide is formed.

When zinc sulfide \((ZnS)\) undergoes roasting, it is heated strongly in the presence of oxygen \((O_2)\). The reaction can be represented as follows:

\[ \text{ZnS} (s) + \text{O}_2 (g) \rightarrow \text{ZnO} (s) + \text{SO}_2 (g) \]

In this reaction:

1. Zinc Sulfide \((ZnS)\): Zinc sulfide is a compound consisting of zinc \((Zn)\) and sulfur \((S)\). When it is heated during roasting, it reacts with oxygen \((O_2)\) from the air.

2. Oxygen \((O_2)\):  Oxygen from the air participates in the reaction. It combines with zinc from zinc sulfide to form zinc oxide and sulfur from zinc sulfide to form sulfur dioxide.

3. Zinc Oxide \((ZnO)\):  Zinc oxide is the product of the reaction. It is a white, powdery compound composed of zinc and oxygen. This compound is often used in various applications, including as a pigment in paints, as a sunscreen ingredient, and in the production of rubber

4. Sulfur Dioxide \((SO_2)\): Sulfur dioxide is another product of the reaction. It is a gas that is released into the atmosphere. Sulfur dioxide is known for its pungent odor and is a common air pollutant produced by various industrial processes.

Roasting is a common method used to extract metals from their ores. In the case of zinc sulfide, roasting converts the zinc sulfide into zinc oxide, which can then be further processed to obtain zinc metal through reduction processes.