Homework Help: Quick Conceptual Question on Ideal Gases

1. Sep 25, 2008

meganw

1. The problem statement, all variables and given/known data

Why is the volume of an ideal gas not important?

I'm just asking this for my own studying benefit, it's not technically "homework", although we are studying it.

My book says that we can draw the fact that the volume of an ideal gas is not important from the fact that an ideal gas is not affected by the identity (structure) of the gas particles..

I don't get it. :-/

Thanks for any help! =)

-Megan

2. Sep 25, 2008

mgb_phys

In an ideal gas you assume that individual particles (atoms/molecules) take up no space.
This is just a cheat to make the maths easier, but for low pressures it is accurate.

There is an advanced form of the gas law equations, Van der Waals equation, which includes addiational terms to account for the volume of the particles and the attraction betwene them.
the difference becomes important at high pressures/densities when the atoms are close together.

3. Sep 25, 2008

meganw

What? How can something have no space?

4. Sep 25, 2008

GCT

Many people are perplexed about the same thing ... it's an approximation. If you are in General Chemistry ignore Van Der Waal.

Ideal gas is in reference to the postulate that the identity of the gas does not matter and that they would not be attracted to each other via intermolecular attractions.

Basically , the point of the argument is that if something is an ideal gas you don't need to worry about the identity of the gas ... if the question claims an ideal gas simply use PV = nRT.

5. Sep 25, 2008

mgb_phys

It's an approximation, it's like ignoring air resistance or the mass of the spring - except it's a very good approximation for stp.