NH3, or ammonia, is classified as a weak base. This classification is based on its ability to partially ionize in water. When ammonia is dissolved in water, it accepts a proton (H+) from water molecules, forming ammonium ions (NH4+) and hydroxide ions (OH−). However, this reaction does not go to completion, meaning that not all the ammonia molecules convert to ions.
In terms of the strength of bases, strong bases fully dissociate in solution, while weak bases only partially dissociate. Because ammonia does not completely ionize, it results in a relatively lower concentration of hydroxide ions compared to a strong base like sodium hydroxide (NaOH), which fully dissociates.
Thus, while NH3 can increase the pH of a solution and demonstrate basic properties, its behavior in aqueous solution characterizes it as a weak base rather than a strong one.