Question

In the following formula, $MgS{O_4}.n{H_2}O$, what does the n before ${H_2}O$ stand for:
A.The number of moles of water
B.The number of moles of hydrogen
C.The mole ratio
D.The number of moles of hydrate
E.The number of moles of anhydrate

Answer 1

Hint:We know that when certain substances are exposed to water present in the atmosphere. They either adsorb it on their surface or have it in their structure producing a complex where water bonds with the cation in ionic substances. The water present in the latter case is known as water of crystallization (or) water of hydration.

Complete step by step answer:We can define hydrates are inorganic salts comprising molecules of water combined in a fixed ratio as an integral part of the crystal which are either attached to the center of metal or that has crystallized with the metal complex. Such hydrates are also said to have water of crystallization or water of hydration.
For example: If the water is heavy water, where the hydrogen is the isotope deuterium, then the term deuterate could be used in place of hydrate.
In the compound $MgS{O_4}.n{H_2}O$, the notation hydrated compound⋅$nH_2O$, where n is the number of water molecules per formula unit of magnesium sulfate, is commonly used to show that a salt is hydrated.
We can say that the value of n is generally a low integer, but there is a possibility that can be fraction even.
We have to know that major hydrates are stable at room temperature. But, few spontaneously lose molecules of water upon standing in the atmosphere, they are said to be efflorescent.
Therefore, the option (A) is correct.

Note:A hydrate which has a lost molecule of water is known as an anhydride. We could remove the remaining water with very strong heating. Anhydrous is the substance that does not contain any water molecules.Few anhydrous compounds are hydrated very easily that they are hygroscopic in nature. We can use them as drying agents or desiccants.