When gypsum is heated at a controlled temperature, how much water remains in the product formed?
Answer and explanation
Correct answer: Half a water molecule per calcium sulphate unit
Gypsum has the formula CaSO₄·2H₂O, so it contains two water molecules per calcium sulphate unit. Controlled heating removes one and a half of these water molecules and forms plaster of Paris, CaSO₄·½H₂O. Therefore half a water molecule remains per calcium sulphate unit. The other values do not match the balanced formula or the known dehydration process, so A is correct.
Frequently asked questions
What is the correct answer to this question?
Half a water molecule per calcium sulphate unit
Why is this the correct answer?
Gypsum has the formula CaSO₄·2H₂O, so it contains two water molecules per calcium sulphate unit. Controlled heating removes one and a half of these water molecules and forms plaster of Paris, CaSO₄·½H₂O. Therefore half a water molecule remains per calcium sulphate unit. The other values do not match the balanced formula or the known dehydration process, so A is correct.
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.
