Washing soda crystals become powdery when kept in open air. This is related to which phenomenon?
Answer and explanation
Correct answer: Efflorescence
The governing concept is water of crystallisation and its loss from a hydrated salt. Washing soda is sodium carbonate decahydrate, Na₂CO₃·10H₂O. On exposure to dry air, its crystals may lose part or all of this combined water and become less crystalline and powdery. This spontaneous loss of water of crystallisation is called efflorescence, so option B is correct. Deliquescence is the opposite type of behaviour, in which a substance absorbs moisture and may dissolve.
Frequently asked questions
What is the correct answer to this question?
Efflorescence
Why is this the correct answer?
The governing concept is water of crystallisation and its loss from a hydrated salt. Washing soda is sodium carbonate decahydrate, Na₂CO₃·10H₂O. On exposure to dry air, its crystals may lose part or all of this combined water and become less crystalline and powdery. This spontaneous loss of water of crystallisation is called efflorescence, so option B is correct. Deliquescence is the opposite type of behaviour, in which a substance absorbs moisture and may dissolve.
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.
