NH4NO3 is called Ammonium nitrate. It is a type of salt. A salt is a product of the reaction of an acid and a base. For NH4NO3, it is a reaction of a weak base and a strong acid. The chemical equation for the formation of NH4NO3 can be written as:
NH4NO3 (aq) ---> NH4+ + NO3-
NH4+ is a conjugate acid of the weak base NH3. It is produced in the dissociation of NH3 in water.
NH3 (aq) + H2O <-----> NH4+ + OH-
NO3- is the conjugate base of the strong acid HNO3. It is produced from the dissociation of HNO# in water.
HNO3 + H2O ---> H3O+ + NO3-