Why does heating gypsum at about 373 K produce plaster of Paris?
Answer and explanation
Correct answer: Gypsum loses part of its water of crystallisation
Gypsum is calcium sulphate dihydrate, CaSO₄·2H₂O. On controlled heating near 373 K, it loses one and a half molecules of water of crystallisation and forms calcium sulphate hemihydrate, CaSO₄·½H₂O, called plaster of Paris: CaSO₄·2H₂O → CaSO₄·½H₂O + 1½H₂O. Thus option A is correct; no calcium metal, chlorine, or sodium carbonate is produced.
Frequently asked questions
What is the correct answer to this question?
Gypsum loses part of its water of crystallisation
Why is this the correct answer?
Gypsum is calcium sulphate dihydrate, CaSO₄·2H₂O. On controlled heating near 373 K, it loses one and a half molecules of water of crystallisation and forms calcium sulphate hemihydrate, CaSO₄·½H₂O, called plaster of Paris: CaSO₄·2H₂O → CaSO₄·½H₂O + 1½H₂O. Thus option A is correct; no calcium metal, chlorine, or sodium carbonate is produced.
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.
