The unfavourable electrochemical reaction among the following is:

Options

A. `Zn+H_(2)SO_(4) to ZnSO_(4)+H_(2)`
B. `KKI+Cl_(2) to KCl+I_(2)`
C. `KCl+I_(2) to KI+IC l`
D. `Al+3HC l to AlCl_(3)+(3)/(2)H_(2)`

Answer

To determine the unfavorable electrochemical reaction among the given options, we will analyze each reaction based on the principles of displacement reactions and the electrochemical series.

### Step-by-Step Solution:

1. **Understanding Displacement Reactions**:
Displacement reactions occur when a more reactive element displaces a less reactive element from a compound. The feasibility of these reactions can be predicted using the electrochemical series.

2. **Analyzing the First Reaction**:
- **Reaction**: Zn + H2SO4 → ZnSO4 + H2
- **Analysis**: Zinc (Zn) is more reactive than hydrogen (H). Therefore, Zn can displace H from H2SO4 to form ZnSO4 and hydrogen gas. This reaction is favorable.

3. **Analyzing the Second Reaction**:
- **Reaction**: KI + Cl2 → KCl + I2
- **Analysis**: Chlorine (Cl2) is more reactive than iodine (I2). Thus, Cl2 can displace I from KI to form KCl and I2. This reaction is also favorable.

4. **Analyzing the Third Reaction**:
- **Reaction**: KCl + I2 → KI + ICl
- **Analysis**: In this case, iodine (I2) is less reactive than chlorine (Cl2). Therefore, I2 cannot displace Cl from KCl. This reaction is not feasible and is unfavorable.

5. **Conclusion**:
Based on the analysis, the unfavorable electrochemical reaction among the options is:
- **KCl + I2 → KI + ICl**

### Final Answer:
The unfavorable electrochemical reaction is **KCl + I2 → KI + ICl**.

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