Energy is released and mass is reduced
NH₄Cl → NH₄⁺ + Cl⁻
NH₄⁺ (the ammonium cation)
Given that the reactants are the very consituents (elements) of the final compound, the enthalpy change of this reaction is the same heat of formation, Hf.
That means that the enthalpy chage for the reaction is -296.8 kj/mol
