The Estimation of Standard Molar Enthalpies of Solution for VOSO4⋅nH2O(s) in Water and in Aqueous H2SO4

Abstract

The molar enthalpies of solution of VOSO4⋅3.52H2O(s) at various molalities in water and in aqueous sulfuric acid (0.1 mol⋅kg−1), ΔsolHm, were measured by a solution-reaction isoperibol calorimeter at 298.15±0.01 K. An improved Archer’s method to estimate the standard molar enthalpy of solution, \(\Delta_{\mathrm{sol}}H^{0}_{\mathrm{m}}\), was put forward. In terms of the improved method, the values of \(\Delta_{\mathrm{sol}}H^{0}_{\mathrm{m}}=-24.12\pm 0.03~\mbox{kJ}{\cdot}\mbox{mol}^{-1}\) of VOSO4⋅3.52H2O(s) in water and \(\Delta_{\mathrm{sol}}H^{0}_{\mathrm{m}}=-15.38\pm 0.06~\mbox{kJ}{\cdot}\mbox{mol}^{-1}\) in aqueous sulfuric acid were obtained, respectively. The data indicates that the energy state of VOSO4 in aqueous H2SO4 is higher than that in pure water.