(150b) Mechanism-Free Chemical Kinetics. Part 3. The Phenolphthalein/Base Reaction

Einstein is quoted as saying that Thermodynamics is the only scientific discipline that will remain unchanged through the millennia.  Why so for Thermodynamics and not for the other scientific disciplines?  The answer is simple: Thermodynamics does not depend on mechanism.  All the other scientific disciplines depend upon hypothesizing a mechanism then comparing experimental results to the results produced by the proposed mechanism.  With time, the proposed mechanisms change: they are either discarded for more relevant ones or they are modified to explain new data or more precise data. Thermodynamics presents mathematical methods for describing changes of state for materials.  In other words, Thermodynamics is mechanism-free.

            The same cannot be said for chemical kinetics.  Currently, we guess a mechanism for a chemical reaction, then compare experimental data to the datum generated by our assumed mechanism.  If the correlation is “good”, then we assume the mechanism is correct and we use it to design a chemical plant.  However, there is no proof that the assumed mechanism is correct.

            Today’s computer power and user-friendly software provide us with the tools to possibly remove mechanism from chemical kinetics.  This paper extends the material presented during the AIChE Spring 2014 and Spring 2015 meetings. This discussion presents new experimental data and expands the discussion for adopting a mechanism-free kinetics in chemical engineering.