Spontaneity of a reaction

[Lauryn Jordan 1F]

In class we discussed rxn or physical change between the change in s and change in h, Dr. Lavelle mentioned that when delta s is negative and delta h is positive it is never spontaneous but the reverse is. does this mean that the reverse of the other 3 would not be spontaneous?

[Chem_Mod]

Hi Lauryn,

Try not to memorize the convention and instead think about the concept. Use the equation . A reaction will be spontaneous whenever < 0. Therefore, it makes sense for a non-spontaneous reaction where is positive and is negative. Use this equation to figure out the different conditions.

[Daniisaacson2F]

I see what you're saying, and I think that it would be easier to just imagine what would make G negative (stated above). But for some of them, the reverse reaction will be the opposite sign of deltaG, changing whether or not it is spontaneous.