Teaching thermodynamics with simple experiments

Simple experiments with the partially miscible system benzyl alcohol:water have been designed to teach basic thermodynamic concepts, such as activity activity coefficient and solubility of nonelectrolytes. By means of a UV sp ectroscopic procedure the aqueous solubility of benzyl alcohol as a functio n of temperature (in the range 25-50 degrees C) and the variation of benzyl alcohol solubility with ionic strength (KCl) were determined. The obtained data were graphically analyzed and the Delta H degrees and Delta S degrees values for the dissolution of benzyl alcohol in water were calculated. The gamma/gamma(o) ratio, which links the activity coefficient of benzyl alcoh ol in a KCI aqueous solution (gamma) with the activity coefficient of alcoh ol in pure water (gamma(o)), was also estimated. The solubility of benzyl a lcohol increases about 5% with 10 degrees C temperature increases, and the gamma/gamma(o) values vary between 1.00 and 1.61 in KCl solutions of increa sing ionic strength (0-1.2 molal).