Question

Copper sulphate crystals which seem to be dry contain water of crystallization. When we heat the crystals, this water is removed and the salt turns white. If you moisten the crystals again with water, you will find that blue colour of the crystals reappears.
The water of crystallization is the fixed number of water molecules present in one formula unit of a salt. Five water molecules are present in one formula unit of copper sulphate. The chemical for hydrated copper sulphate is $CuS{O_4}.5{H_2}O$. Now you would be able to answer the question whether the molecule of \[N{{a}_{2}}C{{O}_{3}}.10{{H}_{2}}O\] is wet. One other salt, which possesses water of crystallization is gypsum. It has two water molecules as a water of crystallization. It has the formula \[CaS{O_4}.2{H_2}O\]. What are the uses of this salt?

Answer 1

Hint: The hydrated salts are formed from the crystallization of its aqueous solution and are in pure crystal form without any contamination. There are two water molecules in gypsum with the formula $CaS{O_4}.2{H_2}O$ which is rich in calcium and sulphate minerals.

Complete step by step answer:
The water of crystallization is defined as the fixed number of water molecules which is present in a one formula unit of a salt. The salt crystals which contain a water of crystallization are called hydrates. The other names used for water of crystallization are water of hydration or crystallization water.
The water of crystallization is formed because purified crystals are obtained from aqueous solution. The crystals formed are pure and free from contamination.
The given compound is hydrated sodium carbonate. The molecular formula of hydrated sodium carbonate is $N{a_2}C{O_3}.10{H_2}O$. In the given formula the 10 \[{H_2}O\] refers to the ten molecules of water which denote the water of crystallization. Therefore, the molecule $N{a_2}C{O_3}.10{H_2}O$ is not wet it is dry.
The other compound with two crystallization is gypsum. The formula of gypsum is $CaS{O_4}.2{H_2}O$.
Gypsum is a sulfate mineral formed of calcium sulfate dihydrate.
The uses of gypsum are shown below.
(1) Gypsum is used as a soil additive which improves the moisture in the soil and helps the soil to work properly.
(2) Gypsum is used as an additive in turbid water which helps the dirt to settle down without damaging the life of aquatic creatures.
(3) Gypsum is added in food as it is rich in calcium.
(4) Gypsum is used as a color additive for cosmetics and drugs.
(5) Gypsum is the primary ingredient used in making toothpaste.

Note: As the salt which contains water of crystallization is also known as hydrates which does not mean that the salt is wet. The water molecule is not joined with the metal cation directly.