What is hydrogen chloride?

Dear student,

Hydrogen chloride is written as HCl. HCl gas is molecular HCl in the gaseous phase and is anhydrous, and HCl acid is HCl in solution with water (an aqueous solution of hydrogen chloride), and can be said to be in the form H+ Cl-.  It is this dissociation of the molecule into constituent ions which gives an acid its properties.

Due to this reason in a chemical reaction written, it appears as HCl(g) or HCl(l).

​​​​​​​Regards