Question

Which of the following is hydrated salt?
A. \[\text{Ca(OH}{{\text{)}}_{2}}\]
B. \[\text{MgC}{{\text{O}}_{3}}\]
C. \[\text{MgS}{{\text{O}}_{4}}\text{.7}{{\text{H}}_{2}}\text{O}\]
D. \[\text{BaC}{{\text{O}}_{4}}\]

Answer 1

Hint: The word hydrated is for the water molecules. That means the molecules which have water molecules attached with their crystalline structure are known as hydrated salts. Whereas those which don't water molecules are anhydrous salt.

Complete step by step answer:
- In the given question we have to find the molecule which is a hydrated salt.
- As we know that salts are those compounds which are made when acid and base react. Along with the salt, water is also formed in this reaction.
- Now, two types of salts are hydrated salt and anhydrous salt.
- Hydrated salt are those salts which consist of a loosely attached water molecule, the no. of water molecules may vary from 1 to 10 or more.
- Whereas the anhydrous salt is those which do not have any loosely attached water molecule.
- Hydrated salt can easily lose the water molecule whereas anhydrous molecule cannot lose water molecule.
- Among the given options, \[\text{MgS}{{\text{O}}_{4}}\text{.7}{{\text{H}}_{2}}\text{O}\] is a hydrated salt because as we can see that there are a total of 7 molecules of water which are loosely attached and can be loosed easily. Hence, option C is the correct answer.
- Whereas in compounds like \[\text{BaC}{{\text{O}}_{4}}\], \[\text{Ca(OH}{{\text{)}}_{2}}\] and \[\text{MgC}{{\text{O}}_{3}}\] does not have any loosely attached water molecule that's why are not considered as hydrated salt.
So, the correct answer is “Option C”.

Note: The process of loss of water molecules from the hydrated salt is known as dehydration. When the water molecules are present in the crystal then it is known as the water of crystallisation or water of hydration.