# Ideal Gas.

jimmy42
I have the variation of the ideal gas equation:

n = PV/RT

Assuming that everything else is equal and only temperature rises that will mean there are more moles than before. Is that right? How can that be?

Thanks for clearing it up.

Mentor
First of all - you got it wrong, if everything stays constant and temperature goes up, n must go down. n is inversely, not directly proportional to T.

If the system is closed, and n is constant, heating the gas will mean pressure goes up. What can you do to lower the pressure?

Homework Helper
Actually it means there will be fewer moles than before, because your formula says you are dividing by T not multiplying by it.

The only way you can keep the pressure and the volume both the same, and increase the temperature, is to remove some of the gas from the system. Think about what Boyle's and Charles's laws say about gases.

jimmy42
OK, thanks. I somehow forgot to do that, yes the pressure will go up.

If the system is closed, and n is constant, heating the gas will mean pressure goes up. What can you do to lower the pressure?

Reduce n?

Mentor
Reduce n?

Exactly. You have to OPEN the system and change it.

cupid.callin
Actually it means there will be fewer moles than before, because your formula says you are dividing by T not multiplying by it.

The only way you can keep the pressure and the volume both the same, and increase the temperature, is to remove some of the gas from the system. Think about what Boyle's and Charles's laws say about gases.

Boyle's and Charles's law donot tell anything about n
its Avogadro's law relating V and n
with this you can relate all others!!!