Solubility is a ubiquitous concept in chemistry, but usually only sparingly soluble salts are examined in the introductory chemistry laboratory. With this two-part experiment, students study more common solubility phenomena. First, solubilities of three ionic salts (NaCl, PbCl2, and KAl(SO4)2.12H2O) in water are measured at four temperatures. The concept of recrystallization is introduced as students cool a high-temperature solution and observe crystal formation. Class data are pooled and students are expected to identify and exclude poor data. Spreadsheet calculations are performed with the group data, which are then graphed, and students observe the wide variance in solubility behavior for the three salts. In the second part of the experiment, water and six organic liquids are mixed pairwise in all possible combinations to determine which pairs are miscible. Dielectric constants are provided for each liquid as a measure of polarity and students are asked to discuss their observed solubilities in terms of polarity. The common rule of "like dissolves like" is found to be less than satisfactory as a description of liquid solubility behavior if too narrowly interpreted.
Supplement
Descriptions of the experimental write-up, instructor's notes, and results/discussion are provided in the supplementaty material.
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