Thermodynamics, Equilibria, and Kinetics

Course Overview

Chem 260 is one of the required introductory core courses for the chemistry major and the biochemistry major, and is a required course for many professional programs in the health sciences. As its name implies, the course covers three topics central to our understanding of reactivity in chemical and biochemical systems: thermodynamics, equilibria, and kinetics.

Thermodynamics is the study of the transfer of energy during a chemical or a biochemical reaction. We know from experience that many reactions are favorable; for example, in a gas furnace the combustion of methane, CH4, in the presence of oxygen, O2, produces carbon dioxide, CO2 and water, H2O,  as products with energy released in the form of heat:

CH4(g) + 2O2(g) → CO2(g) + 2H2O(g) + heat

The reverse reaction (Thankfully!) does not occur; that is, the carbon dioxide we exhale does not react with the moisture in air to produce methane and oxygen. Of particular interest to us is the ability to predict whether a chemical or a biochemical reaction can occur under a given set of conditions. Note that saying a reaction can occur is not the same as saying that it will occur.

Once it begins, a reaction continues until there is no further change in the concentrations of its reactants and products, a condition we call equilibrium. Of particular interest to us is the ability to predict the composition of a system when it reaches equilibrium, and the ability to predict how a system at equilibrium might respond to a change in experimental conditions.

Although we can predict that a reaction should occur and we can predict its final composition at equilibrium, this is not the same as predicting how long it will take (If ever!) to reach equilibrium. For example, thermodynamics tells us that a mixture of methane and oxygen will react to make carbon dioxide and water; a mixture of these two gases, however, is relatively stable unless we first add energy, perhaps by lighting a match. The study of kinetics helps us understand the factors that influence how quickly a reaction occurs. Of particular interest to use is what kinetics can tell use about how a reaction might proceed at a microscopic level.

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