When HCl (hydrochloric acid) and NH3 (ammonia) react, they form ammonium chloride (NH4Cl), a white, water-soluble solid. The reaction between HCl and NH3 can be represented as follows:

HCl + NH3 → NH4Cl

This reaction is an example of an acid-base reaction, where HCl acts as the acid and NH3 acts as the base. During the reaction, the hydrogen ion (H+) from HCl combines with the hydroxide ion (OH-) from NH3 to form water (H2O), while the remaining ammonium ion (NH4+) and chloride ion (Cl-) form ammonium chloride.

The reaction between HCl and NH3 is important in various applications, including the production of fertilizers, pharmaceuticals, and cleaning products. It is also used in laboratories for the preparation of ammonium salts and in qualitative analysis for the detection of ammonia.