Apparent Molal Volumes and Heat Capacities of some Sulfates and Carbonates in Water at 25 C.

摘要

The densities and volumetric specific heats of Na2SO4, K2SO4, MgSO4, Na2CO3, NaHCO3, and NaOH were measured up to an ionic strength of 1 in water at 25 C with a flow densimeter and a flow microcalorimeter. From these data, the heat capacity for the formation of the ion pair MgSO4 was evaluated as 84.9 J K minus 1 mol minus 1. There is an anomalous increase in the apparent molal heat capacities of Na2CO3 at low concentration but the apparent molal volumes are normal. This anomaly can be suppresed with NaOH. Attempts to account quantitatively for this behavior by an hydrolysis correction were not successful. (Author)