The table lists experimental mass solubilities of three compounds in two different…
CHEMISTRY · Multi-part · AP · Chemistry · Properties of Substances and Mixtures · Properties of Substances and Mixtures
Problem
The table lists experimental mass solubilities of three compounds in two different solvents at 25 °C.
Water Ethanol
Compound A 0.020 g 15 g
Compound B 0.12 g 0.25 g
Compound C 45 g 20 g
All three compounds have similar overall molecular mass and polarity indices predicted by a simple additive model. Students are asked to interpret why the data do not align with the polarity predictions.
(a) Rank the compounds in each solvent from most to least soluble based on the table.
(b) For Compound A, propose a specific type of intermolecular interaction with ethanol that could explain its large increase in solubility relative to water.
(c) Compound C contains two ionizable functional groups with pKₐ values near 3 and 9. Explain how partial ionization in water could account for its exceptional aqueous solubility compared with ethanol.
(d) Develop a coherent explanation, integrating parts (b) and (c), that reconciles the observed solubility rankings with the limitations of the simple polarity index model.