Kaplan does appear to use the ‘f, products’ and ‘f, reactants’ phrasing so that part, at least, would appear to be supported (Kaplan 2023-2024, equation 7.9).
The change of delta S and the sum symbol might be merited, though.
Agreed that either way the sum symbol would be useful to add. I actually saw that phrasing in the Kaplan book myself when I went to check this, but I still do think it’s wrong. I am surprised but I think Kaplan might have just made a mistake. Khan Academy doesn’t go over this explicitly, so there’s not much else that’s accepted that I can cite here. I hate to say just google it, but everywhere I’ve looked tells me entropy of formation is rare if ever used at all, so I think it technically exists but would be this an uncommon thing to use.
This is versus the standard molar/absolute entropy, which is the one that is actually taught and used in general in physical chemistry. Every source I’ve found refers to it. But, this change is small anyways and the main core principle is intact that total entropy of products minus reactants is the equation (so people will probably get MCAT questions about this correct whether or not the change is made).
If there’s a content question or practice question that refers to entropy of formation, I must be wrong, but I’d be surprised if it was that and not the commonly used measure, standard molar entropy.
