MediumChemistryHigh School (9–10)GeneralAcids, Bases and Salts › Acids and BasesConceptualBoard Exam
Dry hydrogen chloride gas does not change dry blue litmus paper, but it turns damp blue litmus red…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Dry hydrogen chloride gas does not change dry blue litmus paper, but it turns damp blue litmus red.
- Explain this.
- What would you expect if dry ammonia gas met dry red litmus, and then damp red litmus?
Need a reminder? The key ideaShow
Acids give ions (as ) in water; alkalis give ions. Without water there are no ions. Strong acids split fully, weak acids only a little. Always add acid to water, slowly, never water to acid.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. (a) Hydrogen chloride gives ions only when it dissolves in water. Dry, it has no ions; damp, it does.
Step 2. (b) In the same way, dry ammonia does nothing to dry litmus, but in damp litmus it gives ions and turns red litmus blue.
Answer: acids and bases show their behaviour only in water.
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