Partial molal heat capacities and volumes of electrolytes in nonaqueous solvents and ion–solvent interactions

Abstract

A flow heat capacity calorimeter and a flow vibrating tube densimeter have been used to measure the apparent molal heat capacities and volumes of several alkali metal and tetra-alkylammonium halides in anhydrous N,N-dimethylformamide (DMF), and the standard state partial molal heat capacities and volumes, text-decoration:overlineC0p2 and text-decoration:overlineV02, have been evaluated. A comparison of the data with similar data in water and methanol show that text-decoration:overlineC0p2 for electrolytes in the three solvents behaves quite differently. The alkali metal halides generally exhibit negative heat capacities in water and methanol and positive heat capacities in DMF at 25°C. The temperature dependence of text-decoration:overlineV02 in the three solvents is similar to that of text-decoration:overlineC0p2. Both text-decoration:overlineC0p2 and text-decoration:overlineV02 have been divided into ionic contributions and the values discussed in terms of ion-solvent interactions.