Which of the following reaction in the blast furnace is / are endothermic ?

Options

A. `CaCO_(3) to CaO + CO_(2)`
B. `2C + O_(2) to 2CO`
C. `C + O_(2) to CO_(2)`
D. `Fe_(2)O_(3) + 3CO to 2 Fe + 3 CO_(2)`

Explanation

To determine which reactions in the blast furnace are endothermic, we need to understand the concept of endothermic reactions and analyze the reactions that occur in the blast furnace.

### Step-by-Step Solution:

1. **Define Endothermic Reactions**:
- An endothermic reaction is one that absorbs heat from its surroundings. In terms of enthalpy change (ΔH), these reactions have a positive ΔH value, indicating that the energy of the products is greater than that of the reactants.

2. **Identify Reactions in the Blast Furnace**:
- In a blast furnace, several reactions occur during the extraction of iron from iron ore. The most relevant reactions to consider are:
- The reaction between carbon dioxide and carbon.
- The decomposition of calcium carbonate.
- Other reactions involving the reduction of iron oxides.

3. **Analyze the Reactions**:
- **Reaction 1**: Carbon dioxide (CO₂) reacts with carbon (C) to form carbon monoxide (CO).
\[ \text{CO}_2(g) + \text{C}(s) \rightarrow 2\text{CO}(g) \]
- This reaction is endothermic as it requires heat to proceed, absorbing energy from the surroundings.

- **Reaction 2**: Decomposition of calcium carbonate (CaCO₃) into calcium oxide (CaO) and carbon dioxide (CO₂).
\[ \text{CaCO}_3(s) \rightarrow \text{CaO}(s) + \text{CO}_2(g) \]
- This reaction is also endothermic as it requires heat to break the bonds in calcium carbonate.

4. **Conclusion**:
- The two reactions identified above are endothermic. Other reactions in the blast furnace, such as the reduction of iron oxides, are typically exothermic, releasing heat.

### Final Answer:
The endothermic reactions in the blast furnace are:
1. The reaction between carbon dioxide and carbon to form carbon monoxide.
2. The decomposition of calcium carbonate to form calcium oxide and carbon dioxide.