Question

Hydrated calcium sulphate has the formula of \[CaS{O_4}.2{H_2}O\]
(i) What is the name of the water molecules present in the salt?
(ii) Calculate the percentage of water molecules in hydrated calcium sulphate. \[\left[ {Ca = 40;S = 32;O = 16;H = 1} \right]\]

Answer 1

Hint: We have to know that the water is made up of oxygen and hydrogen gases. And it is prepared by mixing two gases in the presence of sufficient heat. The water has a simple molecular structure which contains one oxygen atom and two hydrogen atoms. And calcium sulphate is a chemical compound having the formula, \[CaS{O_4}.2{H_2}O\]. This is widely used for many purposes in both hydrated and anhydrous form of copper sulphate. And this compound is slightly soluble in water and it is the reason for the permanent hardness of water.

Complete answer:
(i) The name of the water molecules present in the salt is known as water of crystallization. And a salt with the water of crystallization is called hydrate. The hydrogen bond exists in hydrate and it defines the polymeric structure. Hence, the shape of the hydrate is elaborate.
(ii) The percentage of water molecules in hydrated calcium sulphate can be calculated by using the formula,
\[percentage = \dfrac{{mass of water of crystallisation}}{{molar mass of CaS{O_4}.2{H_2}O \times 100}}\]
The mass of water of crystallization \[ = 36g/mol\]
Molar mass of \[CaS{O_4}.2{H_2}O\]\[ = 172g/mol\]. Hence,
\[Percentage Of{H_2}O molecule = \dfrac{{36}}{{172 \times 100}} = 20.9\% \]

Note:
 We need to know that water is a polar compound which is used as an excellent solvent. And the water has a high heat of vaporization and heat capacity. The water is an inorganic compound which does not have any taste and odor. And the water is a volatile liquid which is transparent in nature. The particles present in the liquid are far apart. Hence, it can easily move very easily due to the less intermolecular attraction between the particles.