Entropy change

[Sophie Krylova 2J]

In class we talked about how the reaction proceeds when the change in entropy is positive. Is it referring to the system or the surroundings?

[Anna Okabe]

The reaction is spontaneous if the change in entropy of the universe is positive, and this is the sum of the entropy of the system and the surroundings.

[Justin Chang 2K]

Yes, deltaS(total)=deltaS(system)+deltaS(surroundings). We also talked about how deltaS(surroundings)= -Hsys/T. This is helpful because it tells us an exothermic reaction is usually spontaneous because of the increase in total entropy. The two negatives will cancel, and deltaS(surroundings) will be a positive value, which increases the total entropy and makes the reaction more spontaneous.

[Leah Savage 2F]

Is it true that the entropy of the universe is always increasing because some form of energy is always released by a reaction, even if it's endothermic?

[Joanne Guan 1B]

Yes, entropy is always increasing because even if an endothermic reaction occurs, the energy had to have come from somewhere in order to perform the reaction.