NH4aq
NH4aq denotes the ammonium ion in aqueous solution, NH4+(aq). It is the solvated form of ammonium and the conjugate acid of ammonia (NH3). In water, ammonium participates in the acid–base equilibrium NH4+(aq) + H2O ⇌ NH3(aq) + H3O+(aq). The acid dissociation constant is Ka ≈ 5.6 × 10^-10, corresponding to a pKa of about 9.25 at 25 °C. This means that solutions of ammonium salts are mildly acidic, and the relative amounts of NH4+ and NH3 determine the pH.
NH4+(aq) commonly arises from dissolving ammonia in water or from dissolving ammonium salts such as ammonium
In solution, the ammonium ion is a small, strongly hydrated cation and does not form strong, well-defined
Applications and relevance: NH4+(aq) is a major nitrogen source in agriculture (via ammonium salts and fertilizers)