Chemical equilibrium is a key principal in chemical thermodynamics, but is often a difficult concept for students to grasp.  In our spring semester of General Chemistry, we have developed an introductory laboratory activity involving the reaction between water and CoCl2 in isopropanol to form Co(H2O)62+ to visually demonstrate a system at equilibrium.  CoCl2 dissolved in isopropanol  is deep blue while Co(H2O)62+ is pale red.  Addition of a small amount of water to CoCl2 dissolved in isopropanol produces a purple solution, indicating the presence of both reagent and product and demonstrating a system at equilibrium.  We further use the purple solution to demonstrate key concepts such as chemical reversibility, Le Ch�telier's principle, and the temperature dependence of the equilibrium constant.  As part of the activity, students follow a worksheet that provides critical thinking questions to guide the development of key concepts.

Development of a guided-inquiry laboratory activity to introduce major concepts in chemical equilibrium for general chemistry

243rd National Meeting (2012)

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