Question

Which of the following is not an example of hygroscopic substance?
A.Zinc Chloride
B.Potassium Hydroxide
C.Calcium Chloride
D.Magnesium Chloride

Answer 1

Hydroscopic substances or hygroscopic salts are substances which when exposed to air start to absorb water into it. Epsom salts are not an example of hydroscopic substances.

Complete step by step answer:
Hydroscopic substances or compounds are those that absorb the water from the vapor or the liquid that is present in the environment. Its main application is desiccant. Many of these compounds react chemically with water, some of these compounds are metal hydrides and alkali metals. Many of these compounds take it as water of hydration in the crystal structure. Example of these compounds is sodium sulfate. Water can also be absorbed physically. This sometimes can also be a reversible process and water can be reversed that is de absorbed whereas in some cases it cannot be de absorbed easily. These materials that change into water are mostly salts which have a very powerful affinity for moisture and so they absorb a very large amount of water in it. Some of the examples of these substances are calcium chloride, ferric chloride, magnesium chloride, zinc chloride, potassium carbonate, potassium hydroxide and sodium hydroxide. When these compounds are present in water their properties are modified in comparison to its real and pure state. These modifications are also known as properties of the solution which includes viscosity, electrical conductivity, density etc. $MgC{l_2}$ forms $MgC{l_2}.6{H_2}O$ and $CaC{l_2}$ forms $CaC{l_2}.x{H_2}O,ZnC{l_2}$ forms $ZnC{l_2}.{H_2}{O_n}$ and potassium hydroxide whereas dissolves and it is very difficult to get water out.

Therefore, All the options are correct .

Note: All the salts are not hygroscopic in nature. Pure form of sodium salt that is sodium chloride cannot absorb water from just the atmosphere of the moist air. In low humidity, NaCl can never change.