# Chemistry - Why isn't ΔH = TΔS in ΔG = ΔH - TΔS?

However: $$\Delta S_{sys} = \frac{q}{T}$$, assuming the process is reversible (as usual).

No. $$\Delta S_{env} = \frac{q}{T}$$, assuming the process is reversible (as usual). So you get $$\Delta S_{universe} = -\frac{\Delta G}{T}$$ for a process where the heat exchange with the environment is reversible (and there is no non-PV work).

For more background, see https://chemistry.stackexchange.com/a/114323