Question

Select an incorrect statement with respect to gypsum



1.It is slightly soluble in water

2.it is also known as alabaster

3.On heating gypsum at 373 K , it loses its water molecules and becomes calcium sulphate hemihydrate

4.chemical formula of gypsum is CaSO4. 1/2 H2O​

Answer 1

The incorrect statement is option (4) Chemical formula of gypsum is $CaSO_4.\;\frac12H_2O$

Explanation:

• Gypsum consists of Calcium sulfate and water.
• The chemical formula of gypsum is $CaSO_4.\;2H_2O$, which is Calcium sulfate dihydrate
• The translucent form of gypsum is known as alabaster.
• Moreover, Gypsum is slightly soluble in water
• On heating gypsum at 373 K, it loses one and a half molecules of water and forms calcium sulfate hemihydrate, which is commonly known as  Plaster of Paris.

Applications:

• Gypsum board is mainly used as a finish for walls and ceilings and is known as drywall or plasterboard in construction.
• It is also an ingredient of surgical splints and casting molds.
• The main application of gypsum is that it acts as a retarding agent of cement for regulating the setting time of cement.