Hello everyone. I have a weird question regarding the calculation of free energy changes in a multi-step mechanism. Now, if you have a bunch of calculated free energies in gas phase at 1 atm (say, from an electronic structure program) and you want to model in solvent, you need to get them in a 1M standard state and this requires adding an additional term RT*ln(RT). Now, if every step in your mechanism is either unimolecular or bimolecular, there will be no change in the concentration of anything as the total number of moles of things will all stay constant and these corrections will all cancel when you calculate the delta Gs. However, if you have some mixing of them, such as 1) AB--> A +B 2) B+C->D etc. then in the first case you've added a mole and in the second case you've removed a mole. Therefore, when I calculate the delta G for these steps, the sign of RT*ln(RT) should be positive in the first case and negative in the second case, correct? You won't get cancellation when you calculate the delta Gs and these corrections will tweek things by three or so kcal/mol. Am I on the right track here or am I missing something? Thanks for any help you can give.