Which reaction (s) occurs during calcination
(a) `CaCO_(3)toCaO+CO_(2)`
(b) `2FeS_(2)+(11)/(2)O_(2)toFe_(2)O_(3)+4SO_(2)`
(c ) `Al_(2)O_(3).2H_(2)OtoAl_(2)O_(3)+H_(2)O`
(d) `ZnS+(3)/(2)O_(2)toZnO+SO_(2)`
correct option are

Options

A. a and b
B. b and c
C. a and c
D. b and d

Answer

To determine which reactions occur during calcination, we need to understand what calcination is. Calcination is the process of heating ores in the absence of air or in a limited supply of air to drive off moisture and convert carbonates, hydroxides, or hydrated oxides into their corresponding metal oxides.

### Step-by-Step Solution:

1. **Identify the Process of Calcination**:
- Calcination involves heating ores to remove moisture and convert them into metal oxides. It typically applies to carbonates and hydrated compounds.

2. **Analyze Each Reaction**:
- **(a) `CaCO_(3) → CaO + CO_(2)`**:
- This reaction involves calcium carbonate (CaCO₃), which is a carbonate. Upon heating, it decomposes into calcium oxide (CaO) and carbon dioxide (CO₂). This is a classic example of calcination.
- **Conclusion**: This reaction occurs during calcination.

- **(b) `2FeS_(2) + (11/2)O_(2) → Fe_(2)O_(3) + 4SO_(2)`**:
- This reaction involves iron disulfide (FeS₂), which is a sulfide ore. It is oxidized in the presence of oxygen to form iron oxide (Fe₂O₃) and sulfur dioxide (SO₂). This process is known as roasting, not calcination.
- **Conclusion**: This reaction does not occur during calcination.

- **(c) `Al_(2)O_(3).2H_(2)O → Al_(2)O_(3) + H_(2)O`**:
- This reaction involves aluminum hydroxide (Al₂O₃·2H₂O), which is a hydrated oxide. Upon heating, it loses water to form aluminum oxide (Al₂O₃). This is consistent with the calcination process.
- **Conclusion**: This reaction occurs during calcination.

- **(d) `ZnS + (3/2)O_(2) → ZnO + SO_(2)`**:
- This reaction involves zinc sulfide (ZnS), which is also a sulfide ore. It is oxidized in the presence of oxygen to form zinc oxide (ZnO) and sulfur dioxide (SO₂). This process is also known as roasting, not calcination.
- **Conclusion**: This reaction does not occur during calcination.

3. **Final Conclusion**:
- The reactions that occur during calcination are:
- (a) `CaCO_(3) → CaO + CO_(2)`
- (c) `Al_(2)O_(3).2H_(2)O → Al_(2)O_(3) + H_(2)O`

### Correct Options:
- (a) and (c)