Solubility and solubility product determination of a sparingly soluble salt: A first-level laboratory experiment

摘要

A simple experiment was devised to let students determine the solubility and solubility product, K _(sp), of calcium sulfate dihydrate in a first-level laboratory. The students experimentally work on an intriguing equilibrium law: the constancy of the product of the ion concentrations of a sparingly soluble salt. The determination of solubility is proposed either in an equimolar precipitation of CaSO _4 · 2H _2O, from which the K _(sp) is obtained, or working with an excess of one of the two reagents.