Physical and Theoretical Chemistry


What is the rate constant for a reaction?

The rate constant for a chemical reaction is a quantity that describes how rapidly the reaction proceeds. Rate constants can have different units, depending on how many molecules are involved in the reaction. Consider a simple reaction where a single molecule of a species A becomes a molecule of species B. The rate of the reaction will depend on the concentration of species A (denoted [A]) present, and the rate constant (k) for this reaction. The rate equation for this reaction would be:

This tells us that the reaction rate depends only on the concentration of A, and that the reaction rate will increase as the concentration of A is increased. In truth, the reaction rate also depends on the temperature, pressure, and perhaps other factors as well, but these are all bundled into the rate constant, k.


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