## Midterm question 8 [ENDORSED]

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

Aiden Metzner 2C
Posts: 104
Joined: Wed Sep 18, 2019 12:21 am

### Midterm question 8

On the midterm we were asked how entropy is different based on irreversible expansion or reversible expansion. Is it true that entropy is the same for both since it is a state function?

Renee Grange 1I
Posts: 56
Joined: Fri Aug 30, 2019 12:16 am
Been upvoted: 1 time

### Re: Midterm question 8  [ENDORSED]

In a reversible expansion change in entropy total = 0. Therefore - ΔS surroundings = ΔS system
In an irreversible free expansion ΔS surroundings = 0 and ΔS total = ΔS system

Abigail Sanders 1E
Posts: 112
Joined: Wed Sep 11, 2019 12:16 am

### Re: Midterm question 8

Yes, because entropy is a state function, it does not matter for the change in entropy for the system if it underwent reversible or irreversible expansion. This is why for question 8 you know that for both a and b the change in entropy for the system is 0.910 J/K. The change in total entropy or change in entropy for the universe is not the same for the two reactions, however, as for reversible reactions S(uni)=0 while in irreversible it is >0.

Posts: 103
Joined: Sat Aug 24, 2019 12:15 am

### Re: Midterm question 8

For reversible reactions you know that the energy from the surroundings is equal to the negative of the energy of the system because there is no energy loss in the universe, so it must be equal.

Jaci Glassick 2G
Posts: 104
Joined: Sat Jul 20, 2019 12:16 am

### Re: Midterm question 8

In an isothermal reversible reaction, deltaS total is equal to 0. This means that deltaS surroundings=-deltaS system.
In an isothermal irreversible reaction, deltaS surroundings is equal to 0. This means that deltaS total=deltaS system.
Hope this helps!

Daria MacAuslan 1H
Posts: 50
Joined: Sat Aug 17, 2019 12:16 am

### Re: Midterm question 8

In an irreversible reaction, the total change in entropy will be equal to the change in entropy of the system. In a reversible expansion, the total will be equal to zero, which can also be interpretted as the entropy change of the system is equal to the entropy change of the system but in negative form (deltaSsystem= -deltaSsurr)