Why Is There Partial Pressure If All Molecules Occupy the Same Volume in a Gas?

[crays]

Hi guys, I'm just wondering why is there partial pressure when they said all molecule occupy the same volume in a gas. like in rtp you get 22.4 .

 

[tiny-tim]

Hi guys, I'm just wondering why is there partial pressure when they said all molecule occupy the same volume in a gas. like in rtp you get 22.4 .

Hi crays!

Pressure (which is force per area) is basically the force caused by molecules hitting a (usually imaginary) square metre surface …

so if only 20% of the molecules are oxygen, then the oxygen is supplying only 20% of that force.

Also, as http://en.wikipedia.org/wiki/Partial_pressure#Dalton.27s_law_of_partial_pressures" says …

… ideal gas molecules are so far apart that they don't interfere with each other at all. Actual real-world gases come very close to this ideal.

 

[crays]

Thanks a lot :)