Thermodynamics of alkali alkanoates X. Heat capacities and thermodynamic properties of lithium methanoate and lithium ethanoate at temperatures from ≈ 5 K to 580 K

摘要

Heat capacities of lithium methanoate and ethanoate (CA Registry numbers [556-63-8] and [546-89-4]) have been measured by adiabatic intermittent-heating equilibrium calorimetry from temperatures T near 5 K to 350 K and by differential scanning calorimetry (d.s.c.) from 330 K through melting (solid to isotropic liquid) to 580 K. Smoothed values of Cp,m, [Delta]T0Som, [Delta]T0Hom, and [Phi]om were calculated at selected temperatures, At T = 298.15 K the values are: 8.768[middle dot]R, 9.873[middle dot]R, 1528.6[middle dot]R[middle dot]K, and 4.746[middle dot]R for HCOOLi, and 11.607[middle dot]R, 14.412[middle dot]R, 2065.4[middle dot]R[middle dot]K, and 7.484[middle dot]R for CH3COOLi (R = 8.31451 J[middle dot]K-1[middle dot]mol-1). No transition was observed in the heat-capacity curves of either salt at T T = (495 +/- 1) K, with [Delta]trsHom = (222 +/- 5)[middle dot]R[middle dot]K and [Delta]trsSom = (0.449 +/- 0.07)[middle dot]R was confirmed. The present results are briefly discussed in comparison with those previously obtained on other alkali-metal methanoates and ethanoates.