A thermochemical study of K2M(IO3)4·2H2O(M=Mg2+, Ni2+, Zn2+)

The following reactions:(1)2KIO3+M(IO3)2·nH2O→ΔrHmθK2M(IO3)4·2H2O+(n−2)H2O (MMg2+,Ni2+,Zn2+)were used for the calculation of the enthalpies of the formation of double salts. From the enthalpies of dissolution of iodates and double salts in a calorimetric solvent (water or 3 mol l−1 aqueous HNO3), measured by classical solution calorimetry using an isoperibol reaction calorimeter at 298.2 K. From these values, auxiliary data and by using appropriate thermochemical cycles, the standard molar enthalpy of formation of K2M(IO3)4·2H2O (MMg2+, Ni2+, Zn2+) have been obtained:ΔfHmθ(K2Mg(IO3)4·2H2O, s, 298.2 K)=−2510.68±0.10 kJ mol−1ΔfHmθ(K2Zn(IO3)4·2H2O, s, 298.2 K)=−2198.35±0.10 kJ mol−1ΔfHmθ(K2Ni(IO3)4·2H2O, s, 298.2 K)=−2114.88±0.26 kJ mol−1