A white solid imparts a violet colour to a Bunsen flame. On being heated with concentrated `H_(2)SO_(4)`, the solid gives violet vapours that turn starch paper blue. The salt may be :

Options

A. NaI
B. KI
C. `CaBr_(2)`
D. `MgI_(2)`

Answer

To solve the problem, we need to identify the white solid that imparts a violet color to a Bunsen flame and produces violet vapors when heated with concentrated sulfuric acid, which also turns starch paper blue.

### Step-by-Step Solution:

1. **Identify the Flame Color**:
- The first clue is that the solid imparts a violet color to the Bunsen flame. In qualitative analysis, we know that potassium salts produce a violet flame. Therefore, the solid is likely a potassium salt.

**Hint**: Look for salts that are known to produce a specific flame color when burned.

2. **Consider the Reaction with Concentrated H₂SO₄**:
- When the white solid is heated with concentrated sulfuric acid, it produces violet vapors. This suggests that the solid may release a gas that has a characteristic color. Potassium iodide (KI) is a white solid that, when treated with concentrated sulfuric acid, produces hydrogen iodide (HI) gas, which can appear as violet vapors.

**Hint**: Think about common reactions between metal halides and concentrated acids.

3. **Check the Reaction Products**:
- The reaction of potassium iodide with concentrated sulfuric acid can be represented as:
\[ 2 \text{KI} + \text{H}_2\text{SO}_4 \rightarrow \text{K}_2\text{SO}_4 + 2 \text{HI} \]
- Here, potassium sulfate (K₂SO₄) is formed along with hydrogen iodide (HI), which is responsible for the violet vapors.

**Hint**: Write down the balanced chemical equation to understand the products formed.

4. **Test with Starch Paper**:
- The violet vapors of hydrogen iodide can react with starch paper, turning it blue. This is a characteristic test for iodine, which is released in the form of HI.

**Hint**: Remember that starch paper is used to test for iodine presence.

5. **Conclusion**:
- Based on the flame color, the reaction with concentrated sulfuric acid, and the test with starch paper, we can conclude that the white solid is potassium iodide (KI).

**Final Answer**: The salt may be **KI (potassium iodide)**.