Entropy=enthalpy/T

[Elle_Bertuccelli_1B]

When is the equation [delta]S = [delta]H / T negative? I'm confused because the solutions manual contradicts the formula sheet and I'm not sure which one is right (and how to understand this conceptually).

[Stephanie Demo 2N]

You can also think of that equation as ΔS = q/T as given by the second law of thermodynamics. ΔS will always be positive for a spontaneous reaction, meaning any reaction/change that happens on its own (i.e. volume of a gas expanding when the volume of the container increases). Any non-spontaneous change (i.e. condensation: gas -> liquid, making the system more ordered) will be the result of an outside force acting on it, and it will be -ΔS. Basically, ΔS will be negative whenever the system goes from a more random/disordered state to a more ordered state (another example is water freezing).

[stephanieyang_3F]

Elle, do you mean deltaS(surroundings)=negative deltaH(rxn)/T?