Question

How is gypsum formed?

Answer 1

Hint:Gypsum is a compound which consists of calcium ions and water molecules along with the ions of sulphate attached to each other. For this reason it is also termed as the calcium sulphate hydrate. It is generally white or greyish in colour.

Complete step-by-step answer:In order to answer this question at first we need to know about the basic constituents of it. It is mainly composed of calcium. At first the calcium hydroxide which has the formula $Ca{{(OH)}_{2}}$ or the molecule of calcium carbonate which has the formula $CaC{{O}_{3}}$ are reacted with dilute sulphuric acid which has the formula ${{H}_{2}}S{{O}_{4}}$. The reaction can be chemically represented as,
$CaC{{O}_{3}}(s)+{{H}_{2}}S{{O}_{4}}(aq)\to CaS{{O}_{4}}(s)+C{{O}_{2}}(g)+{{H}_{2}}O(l)$
In this reaction as we can see the calcium carbonate reacts with dilute sulphuric acid in order to form calcium sulphate and carbon dioxide with the release of water. Now, this calcium sulphate molecule would combine with the water molecules in order to form hydrated calcium sulphate. So, the chemical formula of the gypsum becomes $CaS{{O}_{4}}.2{{H}_{2}}O$.
Additional information: The compound gypsum is used in the production of the plaster of paris, as a reactant. It is also used in the production of cement and it could also be used as a drying agent. It is known to be the main component of the chalks we use to write on blackboards.

Note:The number of water molecules present in one mole of gypsum are two. The water which is written in the formula after a dot, is called water of crystallisation and that water could come out of the compound if we heat it.