Question

The aim of the fountain experiment is to prove that:
a.) $HCl$ turns blue litmus red
b.) $HCl$ is denser than air
c.) $HCl$ is highly soluble in water
d.) $HCl$ fumes in moist air

Answer 1

The Fountain Experiment is basically a classic demonstration in which a large round bottomed flask containing a soluble gas such as ammonia is clamped upside down and connected to a trough of water containing an indicator by a glass tube. When a small amount of water is injected to the flask, the gas dissolves creating a lower pressure in the flask, water from the trough is sucked into the flask creating a fountain.

Complete Solution :
A round bottomed flask is filled with a hydrogen chloride in gaseous form. The flask is sealed with a rubber bung through which a glass tube is inserted, drawn to jet on the inside of the flask. The flask is inverted so the glass tube is placed in a beaker of water, the water rising up the tube making a fountain inside the flask.
- During the procedure of the Fountain experiment, as the dropper containing water is squeezed or injected in the flask, a colored fountain is obtained(this testifies the name of the experiment). This shows that $HCl$ gas present in the flask dissolves in water due to its high solubility.
- Hence, the fountain experiment shows us that the $HCl$ gas dissolves in water due its high solubility in it and is acidic in nature as the blue litmus solution turns into a red fountain.
Therefore, the correct option would be (C) $HCl$ is highly soluble in water.
So, the correct answer is “Option C”.

Note: This experiment is generally used to study and observe concepts like solubility and the gas laws, and can also be used to introduce them at the beginner level. It also explains and exemplifies the alkalinity and acidity property of gases. Apart from hydrogen chloride gas $(HCl)$, Ammonia gas $\left( N{{H}_{3}} \right)$ can also be used in the study of fountain experiments .