Differences between an Ideal and Real gas?

Reply Tue 10 May, 2005 02:02 pm
I was just wondering what were some of the differences between real and ideal gases.. I know that ideal gases obey all the gas laws.. and I'm assuming that a real gas doesn't? Help.. someone.. please Confused

Much thanks,
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Reply Tue 10 May, 2005 03:28 pm
All real gases fail to conform to at least on of the set of laws attributed to all gases. So basically they only need to fulfill 90% of the requirements.
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Reply Wed 11 May, 2005 10:46 pm
An ideal gas follows the equation PV=nRT. (in actuality no gasses follow this exactly, but a great many very come close, especially depending on your system's temperature and pressure). A real gas significantly deviates from PV=nRT (the Ideal Gas Law).

To account for this, we throw in a fudge factor "Z" to account for non-ideality. So the equation is now PV=ZnRT. Z is a function of the reduced temperature and reduced pressure of the gas (or gas mixture) at your pressure and temperatue. There are numerous other "equations of state" that you can use to account for non-ideality, but PV=ZnRT is the easiest to do by hand (if you are using any of the canned Process programs you are given a choice between 20 or 30 of them).
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Reply Thu 12 May, 2005 04:05 am
An ideal gas is a monatomic gas with no potential electronic interaction with its neighbors. An ideal gas molecule has mass and velocity (temperature) but no volume. It does not condense, nor does it have a triple point. Helium comes is the closest to being an ideal gas.

Real gasses condense; have electronic interactions, mass, velocity (temperature), and volume. It both condenses and sublimates and has a triple point. Many real gasses behave like ideal gasses over a wide pressure and temperature range.

Ideal gasses obey PV=nRT where Pressure, Volume, Temperature, and molal inventory are variables and R is a gas constant.

This allows comparisons to other ideal gasses by P1V1/(n1T1)=P2V2/(n2T2)

Many other real gas laws exist to compensate for the non-ideal behavior of real gasses (note these will contain many additional variables)*


With 10 points I can describe an elephant; with 11 he'll wag his tail--Euler
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Reply Tue 15 Jul, 2014 07:42 am
1.Ideal gas has no definite volume while real gas has definite volume.

2.Ideal gas has no mass whereas real gas has mass.

3.Collision of ideal gas particles is elastic while non-elastic for real gas.

4.No energy involved during collision of particles in ideal gas. Collision of particles in real gas has attracting energy.

5.Pressure is high in ideal gas compared to real gas.

6.Ideal gas follows the equation PV=nRT. Real gas follows the equation (P + a/V2) (V – b) = nRT.

Reply Tue 15 Jul, 2014 08:49 pm
I got some problems with this.

First; The Van Der Waals equation of state is an improved approximation of the ideal gas law to account for the non-zero volume of an ideal gas but it is still an approximation for real gases.

Second; An ideal gas can have a real molar mass (it set by the real molecular weight of the gas)---n (number of moles=mass of gas divided by its molecular weight)

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Reply Wed 17 Dec, 2014 04:49 am
If you talk about ideal gas then molecules in ideal gas are assumed to be so small that they have no effect except as collision points. But in real gas molecules attract each other, and as the temperature gets near the boiling point
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Reply Sat 28 Nov, 2015 05:53 am
An ideal gas is a theoretical gas composed of a set of randomly-moving point particles that interact only through elastic collisions. The ideal gas concept is useful because it obeys the ideal gas law, a simplified equation of state, and is amenable to analysis under statistical mechanics.

Real gases are gases that do not follow gas law at all temp but only at 0K=-273.15*C above this temp the have forces of attraction between the molecules and r compressible all the gases around us are real gases and ideal gases don't exist as the temperature 0K cannot be achieved in finite number of steps.
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Reply Thu 11 Feb, 2016 12:21 am
Ideal gas has no volume, and no forces of attraction between the molecules. it obeys PV =nRT .
But a real gas has volume, and no forces of attraction between the molecules, and it does not obey PV=nRT
Reply Fri 15 Mar, 2019 07:03 am
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Reply Tue 2 Apr, 2019 11:03 am
Ideal gas: They are hypothetical gases whose molecules occupy negligible space and have no interaction; consequently, they obey the gas law exactly. Distinguish between Real gas and ideal gas: 1. Ideal gas has no definite volume while real gas has a definite volume. 2. Ideal gas has no mass whereas real gas has mass.
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