Abstract
The enthalpies of reaction of Mg(CH3COO)2(c, α), Mg(CH3COO)2(amorph) and Mg(CH3COO)2·4H2O(c) with 1mol dm-3 HCl were measured by an LKB-8700 reaction calorimeter. The following standard enthalpies of formation at 298.15K were determined:
ΔH°f(Mg(CH3COO)2, (c, α)=-(1367.70±0.60),
ΔH°f(Mg(CH3COO)2, amorph)=-(1359.77±0.63),
ΔH°f(Mg(CH3COO)2·4H2O, c)=-(2566.13±0.63)kJ mol-1
The enthalpy changes for the following processes have been calculated:
Mg(CH3COO)2(c)+4H2O(g)→Mg(CH3COO)2·4H2O(c)
ΔHhyd=-(238.4±0.2)kJ mol-1,
Mg(CH3COO)2(amorph)→Mg(CH3COO)2(c)
ΔHcryst=-(7.93±0.16)kJ mol-1.
Homolytic and heterolytic lattice enthalpy of Mg(CH3COO)2 (c) were calculated to be 1148 and 2685kJ mol-1, respectively.
