Raoult’s Law Comparison of Liquid Mixtures Using UV–vis Spectroscopy: A Physical Chemistry Laboratory Experiment

An undergraduate physical chemistry experiment is described
in
which two different liquid mixtures are investigated through UV–vis
spectroscopy to quantify which mixture behaves more ideally. Students
create liquid mixtures of specified mole fractions and then measure
the relative vapor pressure of each compound in the head space above
the mixture using UV–vis spectroscopy. By creating Raoult’s
law plots and fitting the total vapor pressure to a second-order polynomial,
students are able to quantitatively determine that the acetone/toluene
mixture exhibits a higher deviation from ideal behavior when compared
to the acetone/ethyl acetate mixture. Strategies for minimizing error
are outlined which help to ensure consistent experimental results.