Experiment 2 Solubility Density and Melting Point of
Experiment 2 Solubility, Density, and Melting Point of Solids Parts A, B, C, Unknown CHE 116 1
Purpose of This Experiment • Determine the solubility of a solid sample • Calculate the density of a solid sample • Determine the melting point (m. p. ) of a solid with the melting point apparatus • Determine the identity of an unknown by its physical properties (solubility, density, m. p. ) • Work in groups of 2 for the known solid • Work individually for the unknown solid (lab partners must use different unknowns) CHE 116 2
Determination of Solubility • Use only a few crystals of solid • Place the solid in the bottom of a small test tube, add the appropriate liquid, and shake back-andforth gently • If the solid dissolves, it is soluble (s) in the liquid. If the solid does not dissolve, it is insoluble (i) in the liquid. If the solid dissolves a little, but not completely, it is sparingly soluble (sp) in the liquid. CHE 116 3
Density Calculation Density = mass / volume Mass is found with the lab balance (find mass, then find volume of that mass) Volume by difference CHE 116 4
Volume by Difference • Technique used to find the volume of irregularly shaped solids • Put enough liquid into a graduated cylinder, record volume (SF and units) • Add solid sample (of known mass) to this graduated cylinder, record volume (SF and units) • Calculate the volume of the solid (volume liquid and solid – volume of liquid = volume of solid) CHE 116 5
Melting Point Determination • Use the melting point apparatus. Ask for help using the m. p. apparatus. • Crush a few crystals of your sample on weighing paper with the bottom of a test tube. (Press firmly to crush. ) • Put crystals in a capillary tube, then you are ready to use the m. p. apparatus CHE 116 6
Identify Unknown • Determine the density of the unknown solid. • Determine the solubility of the unknown solid. • Determine the m. p. of the unknown solid. (as time permits, choose at least 2 from above) • Identify the unknown solid from list using your determined physical properties. CHE 116 7
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