Which of the following cannot decolourise the iodine solution ?

Options

A. Excess of `Cl_(2)` water
B. Excess of `Na_(2)S_(2)O_(3)` solution
C. Excess of `Br^(-)` solution
D. Excess of `NaOH` solution.

Explanation

To determine which of the given options cannot decolorize iodine solution, we need to analyze the reactions of iodine (I2) with each of the options provided.

### Step-by-Step Solution:

1. **Understanding Decolorization of Iodine Solution**:
- Iodine solution can be decolorized by substances that can react with iodine, typically reducing agents. If a substance does not react with iodine, it will not decolorize the solution.

2. **Analyzing Each Option**:
- Let's denote the options as follows:
- Option A: Cl2 (Chlorine gas)
- Option B: Na2H2O3 (Sodium hydrogen arsenite)
- Option C: Br- (Bromide ion)
- Option D: (Another option not specified)

3. **Option A: Cl2**:
- Chlorine (Cl2) can react with iodine (I2) to form iodide ions (I-) and chloride ions (Cl-). Therefore, Cl2 can decolorize iodine solution.

4. **Option B: Na2H2O3**:
- Sodium hydrogen arsenite (Na2H2O3) is a reducing agent and can also react with iodine, leading to the decolorization of the iodine solution.

5. **Option C: Br-**:
- Bromide ions (Br-) do not react with iodine in a way that would lead to decolorization. There is no significant reaction between Br- and I2, so this option will not decolorize the iodine solution.

6. **Conclusion**:
- Based on the analysis, the option that cannot decolorize the iodine solution is **Option C: Br-**.

### Final Answer:
**Br- cannot decolorize the iodine solution.**

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