Example of redox reaction -

Options

A. `CuSO_(4) + Fe rarr FeSO_(4) + Cu`
B. `Ca(OH)_(2) + 2HCl rarr CaCl_(2) + 2H_(2)O`
C. `CaO+ 2HCl rarr CaCl_(2) +H_(2)O`
D. `CaCO_(3) overset("heat")(rarr) CaO + CO_(2)`

Answer

To identify an example of a redox reaction, we first need to understand what a redox reaction is. A redox (reduction-oxidation) reaction involves the transfer of electrons between two species, where one species is oxidized (loses electrons) and the other is reduced (gains electrons).

### Step-by-Step Solution:

1. **Define Oxidation and Reduction**:
- **Oxidation**: This is the process where a substance loses electrons or gains oxygen. For example, when iron (Fe) is oxidized, it loses electrons and its oxidation state increases.
- **Reduction**: This is the process where a substance gains electrons or loses oxygen. For example, when copper(II) ions (Cu²⁺) gain electrons, they are reduced to copper metal (Cu).

2. **Identify a Redox Reaction**:
- A classic example of a redox reaction is the reaction between copper(II) sulfate (CuSO₄) and iron (Fe):
\[ \text{CuSO}_4 + \text{Fe} \rightarrow \text{FeSO}_4 + \text{Cu} \]
- In this reaction:
- Iron (Fe) is oxidized to iron(II) sulfate (FeSO₄), increasing its oxidation state from 0 to +2.
- Copper ions (Cu²⁺) in copper sulfate are reduced to copper metal (Cu), decreasing their oxidation state from +2 to 0.

3. **Analyze the Reaction**:
- The oxidation half-reaction can be written as:
\[ \text{Fe} \rightarrow \text{Fe}^{2+} + 2e^{-} \]
- The reduction half-reaction can be written as:
\[ \text{Cu}^{2+} + 2e^{-} \rightarrow \text{Cu} \]
- Since there is a transfer of electrons from iron to copper ions, this confirms that the reaction is indeed a redox reaction.

4. **Conclusion**:
- Therefore, the example of a redox reaction is:
\[ \text{CuSO}_4 + \text{Fe} \rightarrow \text{FeSO}_4 + \text{Cu} \]