Question

Write the method of preparation, chemical name and chemical formula of Plaster of Paris.

Answer 1

Hint: Plaster of Paris is a rapidly setting gypsum plaster. It consists of fine white powder which hardens and moistens and is allowed to dry.

Complete step by step answer:Plaster of Paris is first prepared by heating gypsum which if found in Paris. This is the reason why it is called Plaster of Paris. Gypsum is a soft sulphate mineral made up of calcium sulphate dihydrate. Its chemical formula is \[CaS{O_4}.2{H_2}O\].
Preparation of Plaster of Paris;
Plaster of Paris is a chemically hydrated calcium sulphate. It can be prepared by calcining gypsum. Gypsum is an ore of calcium sulphate. Gypsum on heating at ${120^0}C$ gives Plaster of Paris. The chemical reaction is,
$CaS{O_4}.2{H_2}O\xrightarrow{{{{120}^0}C}}CaS{O_4}.\dfrac{1}{2}{H_2}O + \dfrac{3}{2}{H_2}O$
$CaS{O_4}.\dfrac{1}{2}{H_2}O$ is known as Plaster of Paris.
Hence the chemical formula of Plaster of Paris is $CaS{O_4}.\dfrac{1}{2}{H_2}O$ .
Chemical name of Plaster of Paris is Calcium Sulphate Hemihydrate.

Additional information-
Plaster of Paris hardens when mixed with water. It has a wide range of applications. Some of them are,
-It is used in the setting of plaster for fixing broken bones.
-It is used in construction of buildings. Used as protective coating on walls and ceiling.
-It is used as moulding and casting agent for decorative elements.
-It is used to make moulds of teeth in dentistry.
-It is used to make historic monuments and structures.
-It is fire resistant. Hence used in buildings to avoid fire hazards.

Note:
Gypsum can be obtained from Plaster of Paris by mixing Plaster of Paris with water. The chemical reaction is,
$CaS{O_4}.\dfrac{1}{2}{H_2}O + \dfrac{3}{2}{H_2}O \to CaS{O_4}.2{H_2}O$