Synthesis, Characteristics and Standard Molar Enthalpies of Formation of MZn2HPO4PO4 (M=Na+, K+)

Abstract

AbstractMZn2HPO4PO4 (M=Na+, K+) double salts were synthesized by a solid‐state reaction at low temperature and a hydrothermal method, respectively, 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 layered compounds with an isostructure of triclinic system. The decomposition temperatures are 415 and 430 °C by TG, respectively. With the dissolution enthalpies and other standard chemical data, the standard molar formation enthalpies of the MZn2HPO4PO4 (M=Na+, K+) were worked out as follows: =fH⊖m[NaZn2HPO4PO4, s] =(−3042.38±0.31) kJ·mol−1 and =fH⊖m[KZn2HPO4PO4, s] =(−3093.46±0.27) kJ·mol−1.