Do the equilibrium constants have units? A discussion on how general chemistry textbooks calculate and report the equilibrium constants (original) (raw)

International Journal of Physics and Chemistry Education

An analysis of the literature concerning the dimensionality of equilibrium constants reveals that this topic manifests as a controversial issue. Based on this previous examination, this work studies if general chemistry textbooks accurately define and calculate equilibrium constants. In order to evaluate those textbooks, in the first part of this study the experimental equilibrium constants, Kp and Kc, and the thermodynamic equilibrium constant, Kº, are defined. Also, the equations that relate each constant to the other two are given. In the specific presentation of these quantities, an example is discussed both performing their accurate calculation and reporting them using the proper units. In the second part of this study, it is examined the way both first-year university chemistry textbooks and pre-university chemistry textbooks determine equilibrium constants, concentrating on how they handle the units of these quantities. Many textbooks treat Kp and Kc as dimensionless quantities. This misleading assumption is caused by a problem in the terminology used as in many cases Kp (or Kc) plays the role Kº. In order to avoid this misleading treatment of the equilibrium constants some suggestions are provided.