Question

Why is Calcium Sulphate hemihydrate called plaster of Paris?

Answer 1

Hint: Calcium Sulphate hemihydrate is a white- yellowish chemical substance which is present in finely divided powder and it is an odourless powder. Its chemical formula is $CaS{O_4}.\dfrac{1}{2}{H_2}O$ . It has many uses such as, it is used for making sculpture, cast and moulds. It is also known as Gypsum plaster.

Complete answer: So, as we know that, Calcium Sulphate hemihydrate has the chemical formula $CaS{O_4}.\dfrac{1}{2}{H_2}O$ .
Calcium Sulphate hemihydrate is prepared heating Calcium Sulphate dihydrate which is also known as Gypsum. And the temperature required for this reaction is $373K$ to $400K$ .
The reaction for the manufacture process is given below:-
Calcium Sulphate hemihydrate is called plaster of Paris (can be written as POP) because as we have seen in the above reaction, it is formed by heating Gypsum at the temperature $373K$ to $400K$ .
The name plaster of Paris is derived from the large deposits of gypsum in the Montmartre hill in Paris.

Additional information:
There are many uses of plaster of Paris such as:
1) It can be used in the decoration of buildings and monuments.
2) It is used to make the wall paintings.
3) It is used to rejoin the broken bones or fracture so it is used as plaster.
4) It can be used to make the replicas of oral tissues and teeth.
5) It is used in making statues and surgical instruments.

Note:
So, we have concluded that the Calcium Sulphate hemihydrate is called Plaster of Paris because it is formed by heating Gypsum at the temperature $373K$ to $400K$ as we have seen in the preparation reaction. The name is taken from the large deposits of gypsum in the Montmartre hill in Paris.