HCl can exists in two forms. It is either in aqueous or in gaseous form. It can be formed from Hydrogen and chlorine ions or gasses.
Hydrogen Chloride aqueous delta H f = -92.30
Hydrogen Chloride gaseous delta H f = -167.2
examples of production of HCl
Aqueous HCl can be produced in our stomach from Carbon dioxide and Water as starting material.
CO2 + H2O ---> H2CO3
carbonic acid produces proton
H2CO3 <---> H+ + HCO3-
That can combine with the freely floating Cl- ion in the cell thus producing HCl.
Gaseous HCl can be produced via burner process. This is an exothermic reaction.
H2 (gas) + Cl2 (gas) --> HCl (gas)