Abstract
We have measured excess molar isobaric heat capacities for dimethylacetamide (DMAC)+alkane mixtures at 298.15K. The result indicates a W-shaped concentration dependence as predicted from the result of extremely high endothermic excess enthalpies for these mixtures.
The W-shaped dependence arises from a positive non-randomness contribution in excess heat capacity. DMAC molecules have large dipole moment and dipolar interaction acts between them as the intermolecular interaction in the pure state. By mixing with hydrocarbon, this interaction is broken and the more energy is required to weaken the dipolar interaction in the solution state than in the pure state.
