Question

The concentrated HCl acid strongly fumes in ________.
(A) Air
(B) Water
(C) Both
(D) None of these

Answer 1

Hint: Concentrated HCl is a solution of HCl in water where the amount of HCl dissolved in water is very high. When we pour concentrated HCl in water, its concentration will decrease as the amount of solvent increases.

Complete step by step answer:
We need to give the medium in which concentrated hydrochloric acid can give strong fumes.
- Concentrated hydrochloric acid has more % of HCl in the solution and that is the reason why we call it concentrated acid.
- Hydrochloric acid is a polar compound as hydrogen is an electropositive element and chlorine has high electronegativity. Hydrochloric acid is in gaseous form in room temperature as well as in standard temperature (${0^ \circ }C$).
- The reason why HCl is in gaseous form is because its boiling point is $ - {85.5^ \circ }C$.
- So, we know that as the temperature rises above its boiling point, the molecules on the surface of the liquid start to evaporate. Concentrated HCl is a concentrated solution of HCl in water.
- We can say that two phases of HCl are in equilibrium at room temperature which can be shown as below.
     \[HC{l_{(aq)}} \rightleftharpoons HC{l_{(g)}}\]

- Here, the aqueous HCl is the concentrated acid which is there in the vessel and the molecules that get evaporated are shown as $HC{l_{(g)}}$ which gives the fumes.
- So, we can say that Concentrated HCl strongly fumes in the air.
- Now, when we pour concentrated HCl in water, its concentration decreases and the number of HCl molecules present on the surface of the solution decreases. Alongside that they also get solvated in water. As a result we cannot see fumes. Thus, concentrated HCl cannot fume strongly in water.
So, the correct answer is “Option A”.

Note: The fumes of hydrochloric acid are very dangerous and it has corrosive properties. It can damage our eyes, intestine, skin and respiratory organs. That is the reason why concentrated HCl is kept always in fume hood in the laboratory.