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### "Ideal"

Posted: Sat Feb 10, 2018 11:28 pm
When the question or text has the word "ideal", does that mean the system is under constant pressure and temperature?
Also, in terms of "ideal", can the system be open, closed, or isolated?

### Re: "Ideal"

Posted: Sun Feb 11, 2018 1:32 am
Labeling the gases in a system as "ideal" means that the molecules occupy no space and that intermolecular attractions are negligible. We use the concepts of ideal gas laws to approximate the best-case scenario in a system. An ideal system does not have to be under conditions fo constant volume or pressure. However, we can use this information and the ideal gas law, PV = nRT, to solve problems involving ideal gases.

### Re: "Ideal"

Posted: Sun Feb 11, 2018 1:42 am
Since an ideal system does not have to be under constant volume or pressure, does that mean that it does not matter whether it is open, closed, or isolated?

### Re: "Ideal"

Posted: Sun Feb 11, 2018 9:26 pm
Correct me if I'm wrong, but I believe ideal systems can be isolated, open or closed since ideality is normally used to describe the gases in a system, as opposed to the system itself.

### Re: "Ideal"

Posted: Sun Feb 11, 2018 9:33 pm
I believe the term "ideal" is used to describe gases, not systems. Ideal gases are those in which the forces of attraction between the molecules are negligible, and the molecules occupy a very small fraction of the space (taken to be as zero). You must know a gas is ideal before getting involved with any calculations related to the equation PV = nRT.

### Re: "Ideal"

Posted: Tue Feb 13, 2018 5:48 pm
Usually on these tests, we are given the fact that the gases are ideal

### Re: "Ideal"

Posted: Tue Feb 13, 2018 6:02 pm
The point of telling us that a gas is ideal and monoatomic is so that we know we can use the constants Cv= 3/2R and Cp= 5/2R.This allows us to calculate work and entropy when only either volume or pressure remains constant, or the reaction is reversible.