Q&A: Avagadro's Gas Law - Pressure Exerted on or by Gas

[Cheman]

Avagadro's gas law...

Hi,
When talking about Avagadro's gas law ie - all gases at 25 degrees C and 1 atm of pressure will occupy a volume of 24dm3, is the pressure 1 atm outside beinmg excerted on the gas or the pressure being exerted by the gas itself on the walls of its container's insides?
Thanks. :-)

 

[Gokul43201]

It's the latter...pressure exerted on the gas by the walls of the container. However, if there is no container, and the system is open to atmosphere, then the pressure is from the atmosphere (in equilibruim, the pressure exerted by the system on the surroundings is equal to the pressure exerted by the surroundings on the system) and hence will always be about 1 atm...but in an open system, you gas will diffuse into the air and the volume of the gas becomes hard to imagine.

Here's another way to think oabout it. Fill the gas into a balloon. Clearly, the pressure exerted by the gas on the balloon must be 1 atm, since that is the pressure exerted on the balloon by the air outside. Now if the temperature was 25C and there was 1 mole of gas put in the balloon, then its volume will be 24 liters (dm^3).

 

[GCT]

Pressure being exerted by the gas

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