### Delta S

Posted:

**Thu Feb 13, 2020 2:56 pm**What is the difference between Delta S, Delta S (total), and Delta S (surroundings)? How do we apply these concepts on an examination / question?

Created by Dr. Laurence Lavelle

https://lavelle.chem.ucla.edu/forum/

https://lavelle.chem.ucla.edu/forum/viewtopic.php?f=77&t=59342

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Posted: **Thu Feb 13, 2020 2:56 pm**

What is the difference between Delta S, Delta S (total), and Delta S (surroundings)? How do we apply these concepts on an examination / question?

Posted: **Thu Feb 13, 2020 5:00 pm**

Delta S is the change in the entropy of the system. Delta S (surroundings) is the change in entropy of the surroundings. Delta S (total) is Delta S plus Delta S (Surroundings). In a reversible reaction, delta S (surr) is equal to negative Delta S. In an irreversible reaction, Delta S(surr)=0.

Posted: **Sun Feb 16, 2020 3:17 pm**

Delta S is equal to entropy so on a question when asked to calculate entropy you will use a delta s equation. Just normal delta s is the change in entropy, delta s surroundings is the change of entropy in the surroundings, and delta s total is the change of entropy of the surroundings and change of entropy of a system.

Posted: **Sun Feb 16, 2020 3:41 pm**

Delta S of the system is the entropy of the system, Delta S of the surroundings is the entropy of the surroundings (usually just the opposite/negative of Delta S), and the Delta S (total) is 0 for isothermal reversible reactions and is usually equal to Delta S (sys) for irreversible reactions.

Posted: **Sun Feb 16, 2020 6:06 pm**

Delta S (sys) is the entropy of the system, Delta S (surr) is the entropy of the surroundings. Delta S (sys) + Delta S (surr) = Delta S(total), where Delta S (total) is the total entropy of both the surroundings and the system.

Posted: **Sun Feb 16, 2020 9:18 pm**

Delta S - regular delta S, usually concerns the system of the reaction

Delta S (surroundings) - usually equals negative delta S (system)

Delta S (total) - equals delta (system) + delta (surroundings)

Delta S (surroundings) - usually equals negative delta S (system)

Delta S (total) - equals delta (system) + delta (surroundings)

Posted: **Sun Feb 16, 2020 9:33 pm**

Delta S is the entropy of the system. Delta S surroundings is the entropy of the surroundings. Delta S total is the entropy of the surroundings and system combined.

Posted: **Sun Feb 16, 2020 10:19 pm**

Delta S is equal to the entropy of the system whereas delta Ssurroundings is the entropy of the surroundings and so delta Stot is the entropy of the surroundings and system added together.

Posted: **Sun Mar 15, 2020 6:36 am**

When using the equation (delta)S= C ln(T2/T1), How do you know which heat capacity to use?