Thermodynamics of ion pairing of nitrate and chlorate with metal ions in aqueous solution

Abstract

Enthalpies of association of nitrate and chlorate with manganese(II), cobalt(II), nickel(II), copper(II), and zinc(II) have been determined by direct calorimetry in an aqueous medium at 25 °C and ionic strength I= 1 mol dm^–3. The corresponding entropy values have been obtained by using known values of the association constants. The thermodynamic parameters suggest formation of ion pairs of the outer-sphere type, and also indicate the importance of electrostatics in determining the association processes.