Question

A full bottle of concentrated ${{H}_{2}}S{{O}_{4}}$ left uncorked for several days was observed to overflow. This was probably due to ________.
(A) Dissolution of oxygen from the air
(B) Temperature change size of the bottle
(C) Hygroscopic property of sulphuric acid
(D) Reaction between the acid and the bottle

Answer 1

Hint: We know that ${{H}_{2}}S{{O}_{4}}$ is a strong acid. And it can react with electron donating compounds very easily. In an open bottle it is in contact with the environment.

Complete step by step solution:
Sulphuric acid is hygroscopic; it means it attracts water molecules from its vicinity. If the bottle full of concentrated ${{H}_{2}}S{{O}_{4}}$ is kept open in the environment, it will absorb the moisture from the atmosphere.

Its concentration will change and it gets diluted or it may no longer have the exact concentration. Since the volume increases, the acid starts flowing out of the bottle.
This does not happen in dilute sulphuric acid. Since the concentrated sulphuric acid contains more amount of sulphuric acid as compared to concentrated sulphuric acid.
Sulphuric acid absorbs water molecules and the cation ${{H}_{3}}{{O}^{+}}$ is formed. This reaction is a highly exothermic reaction.
So, from the above explanation we can say that option “C” is the correct option.

Note: There are some reasons because sulphuric acid is stored in airtight bottles. Overflow of sulphuric acid, safety reasons, and vaporization, it is not very volatile but still keeping it open can lead to loss of fumes.