Hydrogen chloride is a substance.

1, When this substance is a gas, it is called hydrogen chloride gas, which is pure.

2, When this substance is liquid, it is called liquid hydrogen chloride, which is pure.

3, Hydrochloric acid is an aqueous solution of hydrogen chloride, is a mixture of hydrogen hydride and water.

Liquid hydrogen chloride, gaseous hydrogen chloride is made up of hydrogen chloride molecules. Hydrochloric acid consists of water molecules, hydrogen ions, chloride ions and a small amount of hydroxide ions.