Question

Which of the following salts does not contain water of crystallization?
A) Blue vitriol.
B) Baking soda.
C) Washing soda.
D) Gypsum.

Answer 1

We know that the water of crystallization is the amount of water present in the crystal structure of a compound such that it is present in a stoichiometric amount and can be easily removed on heating the compound.

Complete step by step answer:

Now we discuss how the given options differ from each other.
We know the blue vitriol is also called copper sulfate pentahydrate and the chemical formula is $CuS{O_4}.5{H_2}O$. It has five moles of water. Therefore, the option A is incorrect.

We know the Gypsum is also called calcium sulfate dihydrate and the chemical formula is $CaS{O_4}.2{H_2}O$. It has two moles of water. Therefore, the option D is incorrect. Gypsum is used as a fertilizer and as the main constituent in many forms of plaster and in blackboard chalk.

We know the Washing soda is also called sodium carbonate monohydrate and the chemical formula is $N{a_2}C{O_3}.{H_2}O$. It has one mole of water. Therefore, the option C is incorrect.
Now, we see baking soda,

We know the baking soda is also called sodium bicarbonate and it is an anhydrous salt with water of crystallization and it is used as a dry fire extinguisher because of its alkali nature and the chemical formula is $NaHC{O_3}$.
Therefore, the option B is correct.

Note:
We must remember that anhydrous salts are the salts that do not have water molecules. We also know that the copper sulfate is a hydrated salt that is on heating, loses its water molecules and gives anhydrous copper sulfate.