Hydrothermal Synthesis and Calorimetric Study of Blue Molybdenum Bronze, K0.28MoO3

The hydrothermal heating of H0.28MoO3 in a KCl solution at 431 K led to the formation of a single phase of K0.28MoO3. Hydrated molybdenum bronze was formed as a mid-product during conversion from hydrogen molybdenum bronze to blue bronze. The formation enthalpy of K0.28MoO3 was determined by solution calorimetry to be (delta)fH° (K0.28MoO3, s) = -840.2 kJ mol^-1 at 298.15 K. The enthalpies of the transformation reaction from hydrogen bronze to hydrated bronze and of the formation reaction of blue K0.28MoO3 from hydrated bronze were calculated to be +33 kJ mol^-1 and -48 kJ mol^-1 at 298.15 K, respectively. The calculated enthalpies of the reactions were concordant with the suggested reaction mechanism for a transformation from hydrogen molybdenum bronze to potassium bronze.