Conditions when real gases behave as ideal gases

In summary, when pressure is low and temperature is high, real gases behave almost like ideal gases because the attractive forces in the gas molecules are stronger due to their closer distance, but the fast movement of the molecules compensates for this. The opposite is true for high pressure and low temperature. The assumptions of the kinetic theory state that molecules have negligible size and no intermolecular forces, which holds true for low pressure and high temperature. This results in large intermolecular distances and the gas behaves like an ideal gas. The correction term in the real gas equation, P + an2/V2, accounts for both attractive and repulsive forces. This means that the value of "a" can change depending on the conditions.
  • #1
jd12345
256
2
Well i know real gases behave as ideal gas (almost) when pressure is low and temperature is high. I want to understand this - When pressure is low attractive forces in the gas moelcules will be stronger(as compared to high pressure) but the fast movement due to high temperature compensates it? Am i right?

Why can't it be high pressure and low temperature? Because of high pressure repulsive forces dominate ( because molecules will be very close) but then you lower the temperature and moelcules don't move very fast and that compensates for the repulsive forces

Anything wrong in my reasoning. Please help!
 
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  • #2
Do you remember assumptions used in the kinetic theory?
 
  • #3
Yes - molecules have negligible size
no intermolecular forces
elastic collisions
 
  • #4
No intermolecular forces or negligible intermolecular forces (apart from collisions).

Start from there. What can you say about intermolecular distances in the gas that has a low pressure and a high temp?
 
  • #5
well in case of low pressure and high temperature - there will be large intermolecular distances so negligible intermolecular forces. So it well behave as an ideal gas. I understand now - thank youAnd if there is high pressure there will be repulsive forces and small distances which does not match with the postulates. Thank you again

But one more question - not closely related to my previous question
In the real gas equation pressure is P + an2/V2. Is the correction term only for attractive forces , only for repulsive forces or both? If its for both does that mean value of "a" changes according to conditions
 

FAQ: Conditions when real gases behave as ideal gases

1. What are the conditions when real gases behave as ideal gases?

The conditions when real gases behave as ideal gases are low pressure and high temperature. This means that the gas particles are far apart and have high kinetic energy, causing them to behave similarly to ideal gas particles.

2. What is the main difference between real and ideal gases?

The main difference between real and ideal gases is that ideal gases do not have any intermolecular forces between their particles, while real gases do. This leads to differences in behavior, particularly at high pressures and low temperatures.

3. How does the ideal gas law account for the behavior of real gases?

The ideal gas law, PV = nRT, can be modified to account for the behavior of real gases by incorporating a correction factor, known as the compressibility factor (Z), which takes into account the intermolecular forces present in real gases.

4. Can a real gas ever behave exactly like an ideal gas?

In theory, a real gas can behave exactly like an ideal gas at extremely low pressures and extremely high temperatures. However, in practical situations, this is not achievable and there will always be some deviation from ideal gas behavior.

5. How does the behavior of real gases differ from ideal gases at high pressures and low temperatures?

At high pressures and low temperatures, real gases deviate significantly from ideal gas behavior due to the increased influence of intermolecular forces. This results in a decrease in the compressibility factor and a decrease in the volume of the gas compared to what would be predicted by the ideal gas law.

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