Conductometric Determination of Ion-association Constants for Magnesium and Nickel Sulfates in Aqueous Solutions at Various Temperatures between 0°C and 45°C

Abstract

Thermodynamic equilibrium constants for the ion-association in aqueous solutions of magnesium and nickel sulfates were determined by electrical conductivity measurements at various temperatures between 0°C and 45°C. The standard Gibbs energy and the enthalpy and entropy for the reaction M2++SO42−\ightleftharpoonsM2+·SO42− (M: Mg or Ni) were then calculated from the temperature-dependence of the ion-association constants. The values obtained are as follows: ΔG°298=−2.91 kcal mol−1, ΔH°=2.04 kcal mol−1, and ΔS°298=16.6 cal deg−1 mol−1 for Mg2·SO42−; and ΔG°298=−3.10 kcal mol−1, ΔH°=1.27 kcal mol−1, and ΔS°298=14.7 cal deg−1 mol−1 for Ni2+·SO42−.