Question

A compound X which is prepared from gypsum has the property of hardening when mixed with a proper quantity of water.

1. Identify the compound X.
2. Write the chemical equation for its preparation.
3. For what purpose is it used in hospitals?

Answer 1

1. Compound X is plaster of Paris, or calcium sulphate half-hydrate (CaSO₄.1/2H₂O) 
2. \[\ce{CaSO4 * 2H2O ->[373 K] CaSO4 * 1/2 H2O + 1 1/2 H2O}\]
3. In hospitals, it is primarily used to set fractured or dislocated bones into the correct position. When mixed with the right amount of water, it forms a hard, solid mass that keeps the bone immobilised so it can heal properly. It is also used to make casts and moulds in dentistry.