Single compound phase diagrams are plots that map the pressures and temperatures where two phases are in equilibrium. When two compounds are mixed together, a third axis representing composition is used to depict phase transitions. Due to the increased complexity of these systems, binary phase diagrams are traditionally represented in a piecemeal fashion to students. This obscures the relationship of related properties. The goal of this work is to write an undergraduate physical chemistry laboratory experiment that has student collect both boiling and freezing curves of a system with several complex features and plot a complete binary phase diagram. The system introduced for this experiment is composed of cyclohexane and tert-butanol, which were chosen for their miscibility, ability to form azeotrope and eutectic compositions, low boiling and high melting points, and low toxicity compared to one of the most common systems used for similar laboratories: cyclohexanone and tetrachloroethylene, the former being very caustic and the latter being carcinogenic.

Complete binary phase diagram laboratory for undergraduate physical chemistry courses

253rd National Meeting (2017)

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