Gypsum forms plaster of Paris on controlled heating. If it is overheated, what main problem may occur?
Answer and explanation
Correct answer: Too much water may be removed and the desired hemihydrate will not form
Gypsum is CaSO₄·2H₂O, and controlled heating removes only part of its water of crystallisation to produce plaster of Paris, CaSO₄·½H₂O. If heating is excessive, dehydration can proceed too far and the desired hemihydrate may not be obtained, reducing the material’s useful setting behaviour. Thus option A is correct. The other choices introduce unrelated sodium or chlorine compounds and do not describe gypsum dehydration.
Frequently asked questions
What is the correct answer to this question?
Too much water may be removed and the desired hemihydrate will not form
Why is this the correct answer?
Gypsum is CaSO₄·2H₂O, and controlled heating removes only part of its water of crystallisation to produce plaster of Paris, CaSO₄·½H₂O. If heating is excessive, dehydration can proceed too far and the desired hemihydrate may not be obtained, reducing the material’s useful setting behaviour. Thus option A is correct. The other choices introduce unrelated sodium or chlorine compounds and do not describe gypsum dehydration.
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.
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