Introduction to real gases
Real gases do not always follow the assumptions of the kinetic molecular theory. While the particles of an ideal gas are assumed to occupy no volume and experience no interparticle attractions, the particles of a real gas do have finite volumes and do attract one another. As a result, real gases are often observed to deviate from ideal behavior. Created by Sal Khan.
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- How can a real gas gave high temperatures and low pressures if temperature and pressure are supposed to have a direct relationship?(13 votes)
- Temperature and pressure only have a direct relationship at a constant volume(24 votes)
- When gases(inert gases) in a container attract and when they repel?(6 votes)
- Gases attract one another as soon as they are close enough to "feel" one anothers' electric fields, and repel one another once their electron orbitals come in contact.(3 votes)
- What is the difference between ideal gas and real gas(4 votes)
- The video had said that ideal gas is "No inter-molecular interactions" and "Gas molecular volume negligible". In contrary, the real gas is disturbed by their interactions and their own properties such as volume.( ex: I think not only their volume can disturb. )
It just like the planet wandering in space. If a planet is far away from the others as well as a molecular belonging to the ideal gas and it's focused on its macro movement, we can see it isolated.
But an absolutely isolated system is not exist in real world. So we call it ideal condition. The high-pressure condition needs high temperature or high density. If the temperature is high and the pressure is still low, it proves that the molecular is far away from the others and moving freely at the same time.(4 votes)
- At10:30he says : "The volume of the molecules is starting to become consequential."
I'm seriously lost.
For a given n number of molecules shouldn't the physical volume of the molecules always stay the same ?(2 votes)
- As pressure increases the volume decreases and the proportion of the volume occupied by the molecules goes up. As the proportion goes up the molecular volume starts to have a noticeable effect on the behavior of the gas.
Does that help?(4 votes)
- What are dipole interactions?(2 votes)
- A dipole moment, occurs when the electrons in a covalent bond are pulled closer to one atom than another atom, forming a polar covalent bond. This gives the atom with the electrons closer to it a partial negative charge, and the atom with the electrons further from it a partial positive charge. A dipole interaction is the attraction of the partial positive of one dipole to the partial negative of another dipole.
For information on dipole moments: https://www.khanacademy.org/science/chemistry/chemical-bonds/copy-of-dot-structures/v/dipole-moment(2 votes)
- The gases the having high velocity should exert high pressure. But at5:31you said that gases have high velocity but low pressure. How is that possible?(2 votes)
- high temp with the individual gases possess high velocity but with a relatively bigger container wouldn't give out much pressure.(2 votes)
- How can ideal gas can be a liquid at absolute 0 Kelvin if no inter molecular attraction force is acting between the molecules?(1 vote)
- I assume you're talking about helium? There are no ideal gasses in reality, it's an assumption that works out okay at relative high temperatures but obviously breaks down at low temperatures.(3 votes)
- at the end of the video when comparing behavior at high pressure of ideal and real gases are we saying:
-at high pressure a real gas has greater volume than the ideal gas law would predict?
I understand that the particles will take up more space (aka will not have a negligible volume)(2 votes)
Real gas is not like ideal gas ，the volume can't be ignored
(The ideal gas particles can even pass through each other, the real gas particles are definitely not, so more space is needed)(1 vote)
- How do you tell the deviations of noble gases from the ideal gas behavior?
Thank You!(1 vote)
- Is the volume of real gas the sum of volume of container and the molecules?(1 vote)
- [Instructor] In several other videos, we have talked about the ideal gas law, which tells us that pressure times volume is going to be equal to the number of moles times the ideal gas constant, times the temperature, measured in Kelvin. Now in all of our studies of the ideal gas law, we assumed that the gases that we were dealing with were ideal, And now we're gonna think a little bit about what does it mean to be ideal and what do real gasses, how do they vary from actual ideal gases? Well, in order for us to assume that a gas is ideal, we assume that its volume, the volume that the gas takes up, volume of gas, is negligible, negligible, relative to container, to container. The other thing we assume is that the molecules of the gas don't interact with each other. Molecules don't interact. Now in the real world, we know that all molecules take up some volume, but it could be a reasonable assumption, if we're talking about a really huge container, and we don't have that high a density of molecules in it, it's a reasonable assumption that the volume of the gas itself, that the molecules themselves are small in volume, collectively, relative to the container, and it's reasonable in many circumstances to assume that the molecules don't interact, maybe they don't have strong intermolecular forces, once again, because they're taking up a small portion of the volume. They might even not get close to each other too often. And so that's why these are reasonable assumptions, and they allow us to say that PV is equal to nRT, which is a valuable thing, a valuable approximation in most circumstances. But in the real world, we do know that in actuality, that each molecule takes up some volume, and that if you add up all the molecules together, they're of course going to take up some volume, and if there's enough molecules, or if the container is small enough, we know that the volume of the gas relative to container won't be negligible. We also know that molecules will interact with each other in some way, shape or form. Two molecules can't occupy the same space at the same time, so you definitely have some repulsive forces, and you have, you might have some, even for fairly inert molecules, you might have some temporary dipoles that get formed, some temporary attraction or some temporary repulsion. So if you're dealing with a situation where things are less ideal, and I'm going to make a character of it, where the molecules are taking up a significant volume relative to the container, you can't say that the volume of the molecules are negligible relative to the container, and we assume that they are interacting with each other, they're definitely going to repulse each other, they can't occupy the same space at the same time, but they might attract each other at some points, or repulse each other at other points, and so in this situation, where we can't make these assumptions, we're going to have to modify the ideal gas law.