## Entropy change

Volume: $\Delta S = nR\ln \frac{V_{2}}{V_{1}}$
Temperature: $\Delta S = nC\ln \frac{T_{2}}{T_{1}}$

Sophie Krylova 2J
Posts: 59
Joined: Fri Sep 29, 2017 7:06 am

### Entropy change

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
Posts: 30
Joined: Fri Sep 29, 2017 7:06 am

### Re: Entropy change

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
Posts: 53
Joined: Fri Sep 29, 2017 7:04 am

### Re: Entropy change

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
Posts: 74
Joined: Fri Sep 29, 2017 7:06 am

### Re: Entropy change

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
Posts: 30
Joined: Sat Jul 22, 2017 3:01 am

### Re: Entropy change

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.