Standard Molar Formation Enthalpy of NH4Zn2PO4HPO4 and Its Standard Molar Formation Enthalpy

Abstract

NH4Zn2PO4HPO4 was synthesized by solid-state reaction at low temperature and characterized by XRD, FT-IR, TG and SEM. Thermochemical study was performed by an isoperibol solution calorimeter. According to Hess's law, a new thermochemical cycle was designed. The results show that the obtained products are NH4Zn2PO4HPO4 with layered compound. The decomposition temperatures begin at 303°C, and the final product pyrolyzed at 800°C is Zn2P2O7. With the dissolution enthalpies and other standard chemical data, the standard molar formation enthalpies of the NH4Zn2HPO4PO4 are worked out as follow: ΔfHm[NH4Zn2PO4HPO4, s] = −2943.46 ± 0.757 kJ·mol−1.