Does Temperature Increase Lead to More Moles According to Avogadro's Law?

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Discussion Overview

The discussion revolves around the implications of temperature changes on the number of moles of gas as described by Avogadro's Law and the ideal gas equation. Participants explore the relationships between pressure, volume, temperature, and the number of moles in a closed system.

Discussion Character

  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant asserts that an increase in temperature, with other variables held constant, would lead to an increase in the number of moles (n), questioning how this could be possible.
  • Another participant counters that if temperature rises while keeping pressure and volume constant, the number of moles must decrease, as n is inversely proportional to temperature (T).
  • A different participant reiterates that increasing temperature while maintaining pressure and volume would necessitate the removal of gas from the system, leading to fewer moles.
  • Some participants discuss the implications of Boyle's and Charles's laws, suggesting that they relate to the behavior of gases under changing conditions, while noting that Avogadro's law specifically relates volume and the number of moles.

Areas of Agreement / Disagreement

Participants express disagreement regarding the relationship between temperature and the number of moles, with some asserting that an increase in temperature leads to a decrease in moles, while others propose a different interpretation. The discussion remains unresolved.

Contextual Notes

Participants reference various gas laws (Avogadro's, Boyle's, and Charles's) but do not fully resolve how these laws interrelate in the context of the ideal gas equation. There is a lack of consensus on the implications of temperature changes on the number of moles.

jimmy42
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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.
 
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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?
 
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.
 
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?
 
jimmy42 said:
Reduce n?

Exactly. You have to OPEN the system and change it.
 
AlephZero said:
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 don't tell anything about n
its Avogadro's law relating V and n
with this you can relate all others!
 

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