Why is plaster of Paris used for making casts on fractured bones?
Answer and explanation
Correct answer: It sets hard quickly on adding water
Plaster of Paris is calcium sulphate hemihydrate, CaSO₄·½H₂O. When mixed with water, it rehydrates and changes into gypsum, CaSO₄·2H₂O, forming a hard solid: CaSO₄·½H₂O + 1½H₂O → CaSO₄·2H₂O. Its rapid setting and rigid support help immobilise a fractured bone, so option A is correct.
Frequently asked questions
What is the correct answer to this question?
It sets hard quickly on adding water
Why is this the correct answer?
Plaster of Paris is calcium sulphate hemihydrate, CaSO₄·½H₂O. When mixed with water, it rehydrates and changes into gypsum, CaSO₄·2H₂O, forming a hard solid: CaSO₄·½H₂O + 1½H₂O → CaSO₄·2H₂O. Its rapid setting and rigid support help immobilise a fractured bone, so 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.
