What are the two main reasons for sodium hydroxide becoming wet and less pure in open air?
Answer and explanation
Correct answer: Absorbing moisture and reacting with carbon dioxide
Sodium hydroxide is deliquescent, so it absorbs water vapour from air and becomes wet. It also reacts with atmospheric carbon dioxide to form sodium carbonate: 2NaOH + CO2 → Na2CO3 + H2O. Water absorption changes its physical condition, while carbonate formation lowers chemical purity. Therefore option A gives both reasons; the other choices describe no relevant atmospheric process.
Frequently asked questions
What is the correct answer to this question?
Absorbing moisture and reacting with carbon dioxide
Why is this the correct answer?
Sodium hydroxide is deliquescent, so it absorbs water vapour from air and becomes wet. It also reacts with atmospheric carbon dioxide to form sodium carbonate: 2NaOH + CO2 → Na2CO3 + H2O. Water absorption changes its physical condition, while carbonate formation lowers chemical purity. Therefore option A gives both reasons; the other choices describe no relevant atmospheric process.
Which subject and chapter does this question cover?
This is a Class 10 Science question. Chapter: Chemical Substances – Nature and Behaviour. Topic: Acids, Bases, and Salts.
