Bromine vapours turms ……..paper blue

Options

A. Starch iodide
B. Starch
C. Lead acetate
D. Methyl orange

Answer

To solve the question "Bromine vapours turn ……..paper blue," we need to analyze the options given and understand the chemistry involved.

### Step-by-Step Solution:

1. **Identify the Options**: The options provided are:
- A) Starch iodide
- B) Starch
- C) Lead acetate
- D) Methyl orange

2. **Understand the Reaction**: Bromine (Br2) vapors can react with potassium iodide (KI). In this reaction, bromine displaces iodine from potassium iodide, forming potassium bromide (KBr) and releasing iodine (I2).

The reaction can be represented as:
\[ \text{Br}_2 + 2 \text{KI} \rightarrow 2 \text{KBr} + \text{I}_2 \]

3. **Role of Starch**: Starch is a polysaccharide that forms a blue complex with iodine. When iodine is released from the reaction with bromine, it can react with starch to produce a blue color.

4. **Evaluate the Options**:
- **Starch iodide**: This is a complex of starch and iodide, which will turn blue in the presence of iodine.
- **Starch**: Alone, starch will turn blue in the presence of iodine.
- **Lead acetate**: This does not react with bromine to produce a blue color.
- **Methyl orange**: This is a pH indicator and does not react with bromine to produce a blue color.

5. **Conclusion**: The correct answer is **A) Starch iodide** because bromine vapor reacts with potassium iodide to release iodine, which then reacts with starch iodide to turn the paper blue.

### Final Answer:
Bromine vapours turn **starch iodide** paper blue.

---