The reaction equation between ammonia (NH3) and hydrochloric acid (HCl) is written as follows: NH3+HCl=NH4Cl. Ammonia is a weak base that reacts with hydrochloric acid, forming a compound called ammonium chloride.
During this chemical reaction, hydrochloric acid donates a proton to ammonia, meaning the former compound acts as a Bronsted-Lowry acid, while the latter is a Bronsted-Lowry base. This reaction is often performed to demonstrate the diffusion of gases. For this purpose, the person demonstrating the reaction uses a tube and two cotton pads, one of which is soaked in ammonia and the other in hydrochloric acid. The two pads are placed at the opposite ends of the tube, and approximately a minute later, after the gases have diffused, a ring of ammonium chloride forms.