Question

Name a calcium compound which hardens on wetting with water.

Answer 1

We have to remember that calcium is a compound having the chemical symbol, $'Ca'$ with atomic number $20$. And calcium is an alkaline earth metal which is more reactive. When the calcium is exposed to air there is a formation of a dark oxide nitride layer. The physical properties and chemical properties of calcium are almost similar to the heavier homologous barium and strontium. And the oxidation number of calcium is equal to $+ 2$.

Complete answer:
We need to know that the name of a calcium compound which hardens on wetting with water is Plaster of Paris which is represented as POP. The Plaster of Paris is chemically named to be calcium hydrate hemihydrate and the chemical formula of Plaster of Paris is equal to, $Ca.S{O_4}.\dfrac{1}{2}{H_2}O$. The Plaster of Paris is generally used in many fields. It is mainly used as a decorative coating of walls, used as a protective compound, casting decorative element, used for ceiling and moulding etc. And the Plaster of Paris is used for the interiors of buildings and also used in many external applications.

Note:
The name of calcium compound which hardens on wetting with water is Plaster of Paris which is chemically known as calcium hydrate hemihydrate having the chemical formula, $Ca.S{O_4}.\dfrac{1}{2}{H_2}O$. The Plaster of Paris is a non- combustion and non-flammable material. And the Plaster of Paris has a low chemical reactivity. But it cannot act as an oxidizing agent in the presence of an extreme condition. And in the presence of high temperature, it decomposes and there is a formation of toxic oxide of sulphur.