Conceptual question: Volume in Gas Laws

In summary, the conversation discusses the concept of real volume being greater than ideal volume under real conditions due to the definite volume of molecules. The equation of state for Van der Waals force is mentioned, and it is clarified that the "V" in the equation represents the volume of the container, while "n*b" represents the volume of the molecules. This results in a decrease in the mean free path between molecules, ultimately affecting the real volume. Further information on this topic can be found on the provided Wikipedia link.
  • #1
blueblueblue
5
0
Okay, so I've been trying to wrack my brain around this concept for a while but to no avail.

PV = nRT
(Preal + n2*V-2a)(Vreal - nb) = nRT

From these equations, it's clear that real volume is greater than ideal volume under real conditions. I understand that this is because the molecules have a definite volume, and therefore, Volumereal = Volumecontainer + Volumemolecules.

But on the microscopic level, aren't you more concerned with the mean free path between molecules? So a smaller volume would mean that the gases have a smaller mean free path and vice versa for bigger volumes. In that light, wouldn't taking into account the molecule's volume actually decrease the overall mean free path between molecules, therefore, decrease the real volume? When you include the volume of the molecules, you're essentially decreasing the amount of free space between each molecule, aren't you?

Does that make sense? I'll try to reword it if it doesn't... Thanks!
 
Physics news on Phys.org
  • #2
That equation of state applies to the Van der Waals force. And I think you are confused about the volume term in that equation. The "V" in that equation is the volume of the container. The parameter "n*b" is more like the volume of the actual molecules. That way, the volume of the available free space is (V-nb).

You can read much more about this on http://en.wikipedia.org/wiki/Van_der_Waals_equation
 

1. What is volume in gas laws?

Volume in gas laws refers to the amount of space that a gas occupies. It is one of the four variables in the ideal gas law, along with pressure, temperature, and moles. Volume can be measured in units such as liters, cubic meters, or cubic feet.

2. How does volume affect gas behavior?

The volume of a gas is directly proportional to its pressure and temperature, according to Boyle's and Charles' laws. This means that as volume increases, pressure and/or temperature also increase, and vice versa. Additionally, according to Avogadro's law, the volume of a gas is directly proportional to the number of moles of gas present.

3. What is the relationship between volume and density in gas laws?

Density is defined as mass per unit volume. In gas laws, the density of a gas is inversely proportional to its volume. This means that as volume increases, density decreases, and vice versa. This relationship is described by the ideal gas law, where density is equal to the product of pressure and molar mass divided by the product of temperature and gas constant.

4. How is volume affected by changes in pressure and temperature?

If the amount of gas and moles present remain constant, an increase in pressure or temperature will result in a decrease in volume, and a decrease in pressure or temperature will result in an increase in volume. This relationship is described by Boyle's and Charles' laws, respectively.

5. Can volume be manipulated in gas laws?

Yes, volume can be manipulated in gas laws through changes in pressure, temperature, or the number of moles of gas present. This is the basis of gas law calculations, where one variable is held constant while another is changed to determine the relationship between them.

Similar threads

Replies
5
Views
2K
  • Biology and Chemistry Homework Help
Replies
1
Views
2K
  • Biology and Chemistry Homework Help
Replies
3
Views
6K
  • Chemistry
Replies
1
Views
795
  • Introductory Physics Homework Help
Replies
12
Views
849
  • Mechanical Engineering
Replies
3
Views
953
  • Introductory Physics Homework Help
Replies
18
Views
973
  • Thermodynamics
Replies
20
Views
2K
  • Biology and Chemistry Homework Help
Replies
2
Views
4K
Back
Top