Why does dry HCl gas not change the colour of the dry litmus paper?

Explanation

**Step-by-Step Solution:**

1. **Understanding the Nature of HCl Gas**: Dry hydrogen chloride (HCl) gas is a molecular compound that exists in a gaseous state. It is important to note that in its dry form, HCl does not dissociate into ions.

2. **Role of Litmus Paper**: Litmus paper is used as an indicator to test for acidity or basicity. It changes color in response to the presence of hydrogen ions (H⁺). Blue litmus paper turns red in acidic conditions due to the presence of H⁺ ions.

3. **Absence of Moisture**: For HCl gas to dissociate into H⁺ and Cl⁻ ions, moisture is required. In the absence of moisture, the dry HCl gas cannot ionize, meaning it cannot produce H⁺ ions.

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