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Chemistry

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  • $\begingroup$ Wait even partial pressure of ideal gas depends on their mole ratio which is volume ratio. So you mean they all got the same pressures? $\endgroup$
    – most venerable sir
    Commented Oct 31, 2014 at 3:13
  • $\begingroup$ @Doeser No, that's not what I meant. If I take 2 moles of oxygen and 2 moles of nitrogen and put them in the same container, they will have the same pressure and volume. However, if I have 1 mole of oxygen and 2 moles of nitrogen and I put them in the same container, the gases will have different partial pressures but will have the same volume (the volume of the container.) Mole ratios for gases aren't measured by volume, they're measured by pressure. Check out Dalton's Law of Partial Pressures for more information. $\endgroup$
    – Jason Patterson
    Commented Oct 31, 2014 at 13:21
  • $\begingroup$ But they are proportional according to Avogadro $\endgroup$
    – most venerable sir
    Commented Nov 2, 2014 at 17:07
  • $\begingroup$ @Doeser Avogadro's Law only applies if pressure and temperature are kept constant. That is not the case here, where volume and temperature are constant; that's why they could be canceled in the image from your book. A real life example: I fill a tire with nitrogen until it is at 100kPa pressure. If I then put in an equal number of moles of oxygen, the tire's volume won't increase (much), but the pressure inside the tire will double. The oxygen is filling the same space as the nitrogen. They share a volume, and each has the same partial pressure, 100kPa, and the total gas pressure is 200kPa. $\endgroup$
    – Jason Patterson
    Commented Nov 3, 2014 at 2:18
  • 1
    $\begingroup$ Van der Waals made a model that involved gases that were slightly more real. His model accounted for the volume of the gas particles and the attraction between them. That's all there is to it. Any real gas is a van der Waals system. $\endgroup$
    – Jason Patterson
    Commented Nov 12, 2014 at 2:17