Question

Plaster of paris is prepared from
A. Quick lime
B. Slaked lime
C. Gypsum
D. Lime stone

Answer 1

Hint: Plaster of Paris is a white chemical compound used in making bandages due to its property of quick setting. The molecular formula of Plaster of Paris is \[CaS{O_4}.0.5{H_2}O\]which is obtained from \[CaS{O_4}.2{H_2}O\].

Complete step by step answer:
Plaster of Paris has a wide range of applications in making sculpture and bandages. Plaster of Paris is a white chemical compound with powder like texture. Plaster of Paris is a hydrated calcium sulphate which is obtained by calcining gypsum.
The chemical formula of gypsum is \[CaS{O_4}.2{H_2}O\]. Plaster of Paris is also known as Gypsum plaster.
The formation of plaster of Paris took place when gypsum is heated at 423 k.
The reaction for the formation of Plaster of Paris is shown below.
\[CaS{O_4}.2{H_2}O + Heat \to CaS{O_4}.0.5{H_2}O + 1.5{H_2}O\]
In this reaction one mole of gypsum is heated which gives one mole of plaster of Paris and half mole of water.
On heating gypsum the water molecule is removed and forms a product calcium sulfate hemihydrate. This is known as Plaster of Paris.
The plaster of Paris can again change to gypsum by hydrating. This results in the hardening of plaster.
The Plaster of Paris exists in two crystalline forms one is Calcite and the other is Aragonne. Both of them are insoluble in water but dissolves in the presence of carbon dioxide by forming sodium bicarbonate.
Thus, the Plaster of Paris is prepared from Gypsum.
Therefore, the correct option is C.

Note:
When gypsum is heated at different temperatures different products are obtained. When it is heated as 180 degree Celsius \[\gamma \]-anhydrite is formed and when heated at 250 degree Celsius \[\beta \]-anhydrite is formed which is also known as dead burnt plaster.