Question

Which of the following salts does not contain water of crystallisation?
A. Blue Vitriol
B. Baking Soda
C. Washing soda
D. Gypsum

Answer 1

In the given question it is asked about the given salts of various compounds and the nature of them regarding water of crystallization. In order for a salt to not have water or crystallization it needs to be anhydrous. Now among this only baking soda has that quality so it is the required answer.

Complete step by step solution:
In the given question we have to find out the salt that does not contain water or crystallisation. This in simple terms states that only one salt among the given options have an anhydrous nature. Now an anhydrous molecule is a dried up molecule or in simple terms a molecule that is deprived of any matter molecule in it.
Now we have to provide the chemical formula and details of every option step by step and then we can obtain the right option.
Blue Vitriol: It is a bluish looking copper salt occurring in large crystal forms. Its chemical formula is $CuS{O_4} \cdot 5{H_2}O$.
Baking Soda: Baking soda is white colour salt of the element sodium which has a general existence in anhydrous form without any water or crystallisation. Its chemical formula is $NaHC{O_3}$. It is also widely used on purpose as a dry fire extinguisher because of its alkali nature.
Washing soda: Washing soda is white colour salt of the element sodium which has a general existence in hydrated form with the water of crystallisation. Its chemical formula is $N{a_2}C{O_3}\cdot10{H_2}O$.
Gypsum: Gypsum is white colour salt of the element calcium which has a general existence in hydrated form with the water of crystallisation. Its chemical formula is $CaS{O_4}\cdot2{H_2}O$.

So, the correct option is option B.

Note: Sodium bicarbonate (IUPAC name: sodium hydrogen carbonate), commonly known as baking soda (especially in North America and New Zealand) or bicarbonate of soda, is a chemical compound with the formula $NaHC{O_3}$. Sodium bicarbonate is a white solid that is crystalline, but often appears as a fine powder. It has a slightly salty, alkaline taste resembling that of washing soda (sodium carbonate)