(a) State the method of collecting gases which are denser than air. (b) Name two gases that can be used to perform the fountain experiment in the laboratory...

Answer Details

(a) Collecting gases denser than air

Gases that are denser than air are collected by upward delivery (downward displacement of air): the delivery tube is passed to the bottom of an upright gas jar, and the denser gas sinks and fills the jar from the base upwards, pushing the air out.

(b) Gases for the fountain experiment

Two suitable gases are ammonia (NH₃) and hydrogen chloride (HCl).

The physical property that makes them suitable is their very high solubility in water. When a little water enters the flask of gas, the gas dissolves almost instantly, causing a large drop in pressure inside the flask, so more water is forced up rapidly to form a fountain.