ENTHALPIES OF FORMATION OF THE NEGATIVE-IONS MNO2-, MNO3- AND MNO4- AS DETERMINED BY THE ION-MOLECULE EQUILIBRIUM METHOD

Admixture of potassium chromate to manganese oxide has allowed us to g enerate measurable concentrations of the negative ions MnO2-, MnO3- an d MnO4- in the vapours over manganese oxide at 1300-1500 K. Equilibriu m constants with the participation of these ions have been measured an d the enthalpies of formation {DELTA(f)H-m(degrees)(MnO2-, 0 K)=(-266/-13) kJ mol-1, DELTA(f)H-m(degrees)(MnO3-, 0 K)=(-538+/-14) kJ mol-1, DELTA(f)Hm(degrees)(MnO4-, 0 K)=(-669+/-17)kJ mol-1}, dissociation en ergies and the electron affinity (EA) of MnO2 {EA = 292 kJ mol-1} have been estimated. The use of manganese-containing negative ions to meas ure the activity of manganese oxides is discussed.