Which of the following equations represents calcination ?

Options

A. `2Zn +O_2 rarr 2 ZnO`
B. `MgCO_3 rarr MgO + CO_2`
C. `2Ag + 2HCl + [O] rarr 2AgCl + H_2O`
D. `2ZnS + 3O_2 rarr 2ZnO +2SO_2`

Answer

To determine which equation represents calcination, we need to understand the definition and process of calcination in metallurgy.

### Step-by-Step Solution:

1. **Definition of Calcination**:
- Calcination is a thermal treatment process where concentrated ore is heated in the absence of air. This process is primarily used to remove moisture, carbon dioxide (CO2), or other volatile substances from the ore.

2. **Conditions for Calcination**:
- The heating occurs at a temperature below the melting point of the material being processed.
- It is important that this process occurs in the absence of air to prevent oxidation.

3. **Identifying the Chemical Reaction**:
- We need to analyze the given options to see which one fits the criteria for calcination.
- The general reaction for calcination involves the decomposition of a carbonate ore into an oxide and carbon dioxide.

4. **Evaluating the Options**:
- **Option 1**: 2Zn + O2 → This represents a combustion reaction and does not fit the definition of calcination.
- **Option 2**: MgCO3 → MgO + CO2. This reaction shows the decomposition of magnesium carbonate into magnesium oxide and carbon dioxide, which is a classic example of calcination.
- **Option 3**: (Not provided in the transcript, but we can assume it does not fit the definition).
- **Option 4**: (Not provided in the transcript, but we can assume it does not fit the definition).

5. **Conclusion**:
- Based on the analysis, **Option 2 (MgCO3 → MgO + CO2)** is the correct representation of calcination.

### Final Answer:
The equation that represents calcination is: **MgCO3 → MgO + CO2**.