CHEMISTRY · Multi-part · AP · Chemistry · Properties of Substances and Mixtures · Properties of Substances and Mixtures
Problem
Molecular iodine, I₂, is a highly polarizable non-polar solute. A chemist wishes to dissolve equal amounts of I₂ in three different polar liquids at 25 °C.
The liquids have the following dipole moments (μ):
• Water, H₂O: 1.85 D • Propanone (acetone), (CH₃)₂CO: 2.88 D • Acetonitrile, CH₃CN: 3.92 D
All three liquids have similar molar volumes under the conditions studied.
(a) Rank the three solvent–I₂ systems in order of the expected strength of attractive interactions between the solvent and I₂. Provide the strongest and weakest explicitly.
(b) Offer a detailed explanation for the ranking you provided in part (a), citing specific molecular properties of both the solute and the solvents.
(c) When an excess of solid I₂ is added to each solvent, saturation is reached first in one of the solvents. Identify which solvent reaches saturation first and justify your choice using intermolecular-force considerations.