Question

Which of the following is a highly deliquescent solid?
(A) $FeC{l_3}$
(B) $FeS{O_4}$
(C) $CuS{O_4}$
(D) All of these

Answer 1

As in this question firstly we should clear with the terms Deliquescent solid. So, Deliquescence is the process by which a substance absorbs moisture from the atmosphere unit it dissolves in the absorbed water and then forms a solution. Moreover, relating to solid substances that absorb moisture from the air and become liquid. So, here from the following options we have to find the most highly deliquescent solids.

Complete step by step answer:
As we explained above the definition of deliquescent solids. Furthermore, deliquescent occurs when the vapour pressure of the solution that is formed is less than the partial pressure off the water vapour in the air. Moreover, the solid substance which is obtained by the process of deliquescence is known as deliquescent solid.
So, the example of deliquescent solid is $FeC{l_3}$.
So Anhydrous iron(III) chloride is deliquescent forming hydrated hydrogen chloride mists in moist air. Anhydrous iron(III) chloride Is a fairly strong Lewis acid, and it is used for the catalyst in organic synthesis.
In $CuS{O_4}$, few ionic compounds will take so much water from the atmosphere that they may eventually dissolve in their water of hydration, so these substances are also called deliquescent.

So, the correct answer is Option A.

Additional information:
Certain liquid substances absorb water from the air to get diluted, these are also regarded as being hygroscopic. And if a high hygroscopic substance absorbs so much moisture than an equal solution Is formed, so the substance becomes deliquescent. Moreover, Gypsum Is neither hygroscopic salt or deliquescent salt. Gypsum is also not a deliquescent salt as it does not form its solution by absorbing water from the surroundings. Gypsum is somewhat soluble in water. So when it is applied to the soil, it's solubility depends on several factors, including particle size, soil moisture.

Note: Most of the deliquescent substances are salts. While ($NaCl$) Sodium Chloride Maybe deliquescent if the particles smell and the humidity is very high. So, mostly salt is usually considered to be hygroscopic. Just because of their affinity for water, deliquescent substance use as desiccants.