Thermochemistry of the aqueous manganous ion

Abstract

Heats of solution of MnS04(c) have been measured and combined with heats of dilution to yield AH0 = -15.3 kcal/mole for the standard heat of solution. This value leads to AH,' = -52.9 kcal/~nole for Mn2+(aq). Calculations with data from theliterature give AGrO = -55.1 kcal/mole for Mn2+(aq).Combination of this value with our AHfO gives SZ0 = -16.2 gibbs/mole for MnZ+(aq). Our AHfO value for Mn2+(aq) is compared with other values derived fro111 calculations based on data taken from the literature.

Improvements in Estimated Entropies and Related Thermodynamic Data for Aqueous Metal Ions

“…First, by updating the value obtained from the heat of solution of manganese in acid, we obtain Δ H f ○̵ (Mn 2+ ,aq) = −222.4 kJ mol –1 . Secondly, Gedansky and Hepler’s revision of earlier work gives Δ H f ○̵ (MnSO 4 , s) = −1066.5 kJ mol –1 . We have extrapolated heats of solution at high dilution , to infinite dilution using Pitzer’s theory and obtained Δ H ○̵ sol (MnSO 4 , s) = −64.6 kJ mol –1 .…”

“…Secondly, Gedansky and Hepler’s revision of earlier work gives Δ H f ○̵ (MnSO 4 , s) = −1066.5 kJ mol –1 . We have extrapolated heats of solution at high dilution , to infinite dilution using Pitzer’s theory and obtained Δ H ○̵ sol (MnSO 4 , s) = −64.6 kJ mol –1 . This gives Δ H f ○̵ (Mn 2+ ,aq) = −221.8 kJ mol –1 .…”