Why may washing soda crystals gradually appear like a white powder when left exposed to air?
Answer and explanation
Correct answer: Because they can lose water of crystallisation
Washing soda is sodium carbonate decahydrate, Na₂CO₃·10H₂O, so its crystals contain water of crystallisation. When exposed to dry air, some of this water may be lost through efflorescence. The hydrated crystals then lose their clear crystalline appearance and may become opaque, crumbly, or powder-like. Therefore, option A is correct; no hydrogen gas, copper sulphate, or acid is formed.
Frequently asked questions
What is the correct answer to this question?
Because they can lose water of crystallisation
Why is this the correct answer?
Washing soda is sodium carbonate decahydrate, Na₂CO₃·10H₂O, so its crystals contain water of crystallisation. When exposed to dry air, some of this water may be lost through efflorescence. The hydrated crystals then lose their clear crystalline appearance and may become opaque, crumbly, or powder-like. Therefore, option A is correct; no hydrogen gas, copper sulphate, or acid is formed.
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.
