Separating a Synthetic Pain Relief Mixture—Inquiry Lab Kit for AP® Chemistry

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Big Idea 3, Investigation 9, Primary Learning Objective 3.10. Most over-the-counter drugs consist of mixtures, or physical blends, of active drug ingredient(s) and binders. The main characteristic of a mixture is that it has a variable composition—the components of the mixture may be present or mixed in varying proportions. The substances in a mixture retain their distinctive chemical identities, as well as some of their unique physical properties. The purpose of this investigation is to study the physical properties of ingredients in a synthetic pain relief mixture and determine its percent composition. The lab begins with an introductory activity to test the solubility of each possible component in an organic solvent, ethyl acetate, and in a basic aqueous solution of sodium bicarbonate. The results provide a model for the guided-inquiry design of a flow chart that will map the procedure used to separate components in a mixture and determine percent composition. Optional extension activities include varying the amounts of individual components in the synthetic mixtures and analyzing consumer samples. Students may also measure the melting points of the isolated components, acetylsalicylic acid and acetaminophen, to confirm their identity. This advanced inquiry lab enforces understanding of solubility and chemical reactions as students carry out their own step-by-step experiments and work collaboratively with their peers. Complete for 24 students working in pairs. Perform this experiment in a fume hood or well-ventilated lab. Common laboratory equipment is required and available separately.