Which one of the following halogents turn (s) strach iodide paper blue ?

Options

A. `CI_(2)`
B. `Br_(2)`
C. `I_(2)`
D. `F_(2)`

Explanation

To determine which halogen turns starch iodide paper blue, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Reaction**:
- Starch iodide paper contains iodide ions (I⁻). When a halogen is introduced, it can oxidize these iodide ions to iodine (I₂).

2. **Identifying the Halogens**:
- The halogens in question are typically chlorine (Cl₂), bromine (Br₂), and iodine (I₂). We need to identify which of these can oxidize iodide ions.

3. **Chlorine Reaction**:
- Chlorine (Cl₂) is a strong oxidizing agent. When it comes in contact with potassium iodide (KI) on the starch iodide paper, it oxidizes iodide ions to iodine:
\[ Cl_2 + 2KI \rightarrow 2KCl + I_2 \]
- The released iodine (I₂) then reacts with starch to form a blue-black complex.

4. **Bromine Reaction**:
- Bromine (Br₂) can also oxidize iodide ions. The reaction is as follows:
\[ Br_2 + 2KI \rightarrow 2KBr + I_2 \]
- Similar to chlorine, the iodine produced will react with starch to give a blue-black color.

5. **Iodine Reaction**:
- Iodine (I₂) does not oxidize iodide ions; therefore, it will not turn starch iodide paper blue.

6. **Conclusion**:
- Both chlorine (Cl₂) and bromine (Br₂) can turn starch iodide paper blue. Thus, the correct options are chlorine and bromine.

### Final Answer:
Chlorine (Cl₂) and Bromine (Br₂) turn starch iodide paper blue.

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