Question

The number of molecules of water of crystallisation present in washing soda crystals is
A) five
B) two
C) ten
D) seven

Answer 1

We have to remember that the chemical formula of washing soda is${\text{NaC}}{{\text{O}}_{\text{3}}}{\text{.10}}{{\text{H}}_{\text{2}}}{\text{O}}$. This washing soda plays a major role in the industrial process. This washing soda is prepared by Solvay process. The washing soda is prepared by using ammonia, water, sodium chloride and Carbon dioxide. The preparation of washing soda two main factors are main. One is solubility and the other is isolation.

Complete answer:
We also know that the general chemical formula of washing soda is ${\text{NaC}}{{\text{O}}_{\text{3}}}{\text{.10}}{{\text{H}}_{\text{2}}}{\text{O}}$. It is a crystallized form. From free form to crystalline form it requires some amount of water. The chemical formula of free form of washing soda is ${\text{NaC}}{{\text{O}}_{\text{3}}}$. But this free form of washing soda is not stable. Hence, we convert into crystalline form. In crystallisation technique, we use solvent for dissolution of washing soda and anti-solvent used for crystals formation.
The chemical reaction of crystallisation of washing soda is given below,
${\text{NaC}}{{\text{O}}_{\text{3}}}{\text{ + n}}{{\text{H}}_{\text{2}}}{\text{O}} \to {\text{NaC}}{{\text{O}}_{\text{3}}}{\text{.10}}{{\text{H}}_{\text{2}}}{\text{O}}$
Now, it is a dehydrated form. Then only it is forming proper crystallized nature. The washing soda in monohydrate form means it completely converts into crystal to white ash.
Hence, ten molecules of water of crystallisation present in washing soda.

Note:
We must remember that the washing soda is mainly used for laundering purposes. Washing soda is also used for laboratory purposes also. In qualitative analysis and volumetric analysis also washing soda is used. Washing soda is also used in water treatment. It is used for converting hard water to soft water. The washing soda is also used for manufacturing of paper, glass and paints.