Why is gypsum heated at a controlled temperature rather than at too high a temperature?
Answer and explanation
Correct answer: To remove the right amount of water and form Plaster of Paris
Gypsum is calcium sulfate dihydrate, CaSO4·2H2O, so it contains water of crystallisation. Controlled heating removes about three-fourths of this water and produces Plaster of Paris, CaSO4·1/2H2O. If heating is excessive, the remaining water can also be removed and anhydrous calcium sulfate may form, which does not set properly with water. Therefore option A is correct.
Frequently asked questions
What is the correct answer to this question?
To remove the right amount of water and form Plaster of Paris
Why is this the correct answer?
Gypsum is calcium sulfate dihydrate, CaSO4·2H2O, so it contains water of crystallisation. Controlled heating removes about three-fourths of this water and produces Plaster of Paris, CaSO4·1/2H2O. If heating is excessive, the remaining water can also be removed and anhydrous calcium sulfate may form, which does not set properly with water. Therefore option 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.
