How is plaster of paris prepared?How does it react with water?
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Calcium sulphate with half a molecule of water per molecule of the salt (hemi-hydrate) is called plaster of paris (plaster of paris).
Preparation
plaster of paris is prepared by heating gypsum (CaSO4.2H2O) at 120°C in rotary kilns, where it gets partially dehydrated.

The temperature should be kept below 140°C otherwise further dehydration will take place and the setting property of the plaster will be partially reduced.
Properties
It is a white powder. When mixed with water (1/3 of its mass), it evolves heat and quickly sets to a hard porous mass within 5 to 15 minutes. During setting, a slight expansion (about 1%) in volume occurs so that it fills the mould completely and takes a sharp impression. The process of setting occurs as follows:

The first step is called the setting stage, and the second, the hardening stage. The setting of plaster of Paris is catalyzed by sodium chloride, while it is reduced by borax, or alum.
Uses
In surgery for setting broken or fractured bonesFor making casts for statues, in dentistry, for surgical instruments, and toys etcIn making black board chalks, and statuesIn construction industry
Preparation
plaster of paris is prepared by heating gypsum (CaSO4.2H2O) at 120°C in rotary kilns, where it gets partially dehydrated.

The temperature should be kept below 140°C otherwise further dehydration will take place and the setting property of the plaster will be partially reduced.
Properties
It is a white powder. When mixed with water (1/3 of its mass), it evolves heat and quickly sets to a hard porous mass within 5 to 15 minutes. During setting, a slight expansion (about 1%) in volume occurs so that it fills the mould completely and takes a sharp impression. The process of setting occurs as follows:

The first step is called the setting stage, and the second, the hardening stage. The setting of plaster of Paris is catalyzed by sodium chloride, while it is reduced by borax, or alum.
Uses
In surgery for setting broken or fractured bonesFor making casts for statues, in dentistry, for surgical instruments, and toys etcIn making black board chalks, and statuesIn construction industry
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Answered by
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Plaster of Paris is prepared by heating gypsum [which is chemically calcium sulphate dihydrate (CaSO4.2H2O)] at 373 K. On heating at 373 K, gypsum loses water molecules and becomes Plaster of Paris, which has the chemical name calcium sulphate hemihydrate. Its chemical formula is CaSO4.1/2H2O.
when it is added in water then it makes gypsum
CaSO4.1/2H20+1¹/2H2O= CaSO4.2H2O
when it is added in water then it makes gypsum
CaSO4.1/2H20+1¹/2H2O= CaSO4.2H2O
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