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Why does dry HCl gas not change the colour of the dry litmus paper?
Answer:
- Litmus paper shows change in colour only in the presence of H + ions.
- Acids dissociate to give H + ions only in the aqueous solution.
- Dry acid does not dissociate to give H + ions.
- In this case HCL is not in aqueous form nor is the litmus paper wet and thus the lack of presence of H + ions leads to the litmus paper not changing its colour.
