VANADIUM(V) EQUILIBRIA - SPECTROPHOTOMETRIC AND ENTHALPIMETRIC INVESTIGATION OF THE DIMERIZATION AND DEPROTONATION OF HVO42-

The dimerization and deprotonation of HVO4(2-) have been investigated in 1 M Na(Cl) medium at 25-degrees-C. Spectrophotometric and calorimetric measurements were made at [OH-] greater-than-or-equal-to M, where all other vanadate(V) hydrolysis equilibria could be neglected. Equilibrium constants and other thermodynamic quantities have been determined: for the dimerization of HVO4(2-) log K(d) = 0.83, DELTA-H0 = - 28 kJ mol-1 and T-DELTA-S0 = -24 kJ mol-1, and for the ionization log K = -13.29, DELTA-H0 = 24 kJ mol-1 and T-DELTA-S0 = -52 kJ mol-1.