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Homework Help: PV = nRT problem

  1. Sep 11, 2008 #1
    The total pressure of a mixture of oxygen and hydrogen is 1 atm. The mixture is ignited and the water is removed. The remaining gas is pure hydrogen and exerts a pressure of 0.4 atm when measured at the same values of T and V as the original mixture. What was the composition of the original mixture in mole percent?

    I started by using the equation P=nRT/V. Since the V, R and T are the same before and after the reaction I solved the equation for P/n = RT/V so the two equations (for before and after the reaction) could be set equal to each other. Then I got stuck! Please Help!
  2. jcsd
  3. Sep 11, 2008 #2


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    Staff: Mentor

    This is not advanced physcis, but basic chemistry.

    In what molar ratio do hydrogen and oxygen react?

    There ir 0.4 atm of hydrogen left. 0.6 atm of mixture was consumed.
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