Dissertations from ProQuest

Title

Apparent molar heat capacities of dilute methanol solutions from 298 to temperatures approaching the critical temperature

1987

Article

Degree Name

Doctor of Philosophy (Ph.D.)

Chemistry

First Committee Member

Cecil Criss, Committee Chair

Abstract

The apparent molar heat capacities of a select group of electrolytes and nonelectrolytes in methanol have been measured from 298 K to 503 K using a high-temperature high-pressure flow heat capacity calorimeter. Partial molar heat capacities at infinite dilution (C$\sb{\rm p2}\sp\circ$) were obtained for nonelectrolyte solutions by a linear extrapolation to infinite dilution. A fitting as a function of temperature, employing a theoretically derived nonclassical critical exponent, was performed. The divergence patterns were explained in terms of solute-solvent interactions, and extrapolations to other near-critical and supercritical phenomena were made.C$\sb{\rm p2}\sp\circ$ were also determined for the electrolyte solutions, this time employing theoretically derived Debye-Huckel limiting law slopes to extrapolate plots of the apparent molar heat capacity vs. square root of molality to infinite dilution. The divergences of C$\sb{\rm p2}\sp\circ$ as the critical point was approached were explained in terms of the strong solute-solvent interactions characteristic of electrolyte solutions. An analysis was made using the Born dielectric continuum model, and good agreement between the model and the experimental results indicated classical electrolyte behavior.

Keywords

Chemistry, Physical