Do the equilibrium constant(s) have units?

Abstract

This paper reports some incorrect assumptions that many teachers and general chemistry textbooks hold when dealing with equilibrium constants. After presenting the proper definition of both the experimental constants, Kp and Kc, and the thermodynamic constant, Kº, the usual misrepresentations related to these terms are analysed. Many textbooks confuse Kp with Kº and also state that both Kp and Kc are dimensionless. One problem is proposed and solved in order to exemplify a correct treatment of the quantities involved.