The author replies to Lunelli.

Professor Lunelli has pin-pointed a flaw in “Let’s Drive ‘Driving Force’ Out of Chemistry” (1). The italicized part of the second sentence he quotes anticipates the comment about the application of ∆G to irreversible processes in the succeeding sentence and misleadingly points back to the preceding sentence about reversible processes. Reversible processes are limiting cases, in which T_sys = T_surr and P_sys = P_surr throughout for common processes. Thus, temperature and pressure are indeed constant for reversible processes of the type under consideration.

Literature Cited

1. Craig, N. C. J. Chem. Educ. 2005, 82, 827–828.