Roasting is carried out to :

Options

A. convert sulphide to oxide and sulphate
B. remove water of hydration
C. melt the ore
D. remove arsenic and sulphur impurities

Answer

### Step-by-Step Solution

1. **Understanding Roasting**: Roasting is a metallurgical process that involves heating ores in the presence of excess air (oxygen) at temperatures below their melting point. This process is primarily used for sulfide ores.

2. **Conversion of Sulfide to Oxide**: The main purpose of roasting is to convert metal sulfides into metal oxides. For example, when a metal sulfide (like zinc sulfide, ZnS) is roasted, it reacts with oxygen to form zinc oxide (ZnO) and sulfur dioxide (SO2) gas. The general reaction can be represented as:
\[ \text{Metal Sulfide} + \text{O}_2 \rightarrow \text{Metal Oxide} + \text{SO}_2 \]

3. **Removal of Water of Hydration**: Roasting can also be used to remove water of hydration from hydrated ores. When hydrated ores are heated, the water molecules are expelled, leading to the formation of anhydrous ores.

4. **Removal of Impurities**: During the roasting process, impurities such as arsenic and sulfur are removed as volatile oxides. For instance, sulfur is released as sulfur dioxide (SO2), which is a gas and can easily escape from the reaction mixture.

5. **Not for Melting Ores**: It is important to note that roasting is not primarily aimed at melting the ore. Instead, it prepares the ore for further processing by converting it into a more suitable form for extraction of the metal.

6. **Conclusion**: Therefore, the main purposes of roasting include:
- Converting sulfide ores to oxide ores.
- Removing water of hydration from hydrated ores.
- Removing impurities like arsenic and sulfur.

### Final Answer
Roasting is carried out primarily to convert sulfide ores to oxide ores.