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Homework Help: Ideal Gas Law solve for partial pressure

  1. Aug 12, 2014 #1
    1. Gaseous compound Q contains only xenon and oxygen. When 0.100 g of Q is placed in a 50.0 mL steel vessel at 0 °C, the pressure is 0.229 atm. When the vessel and its contents are warmed to 100 °C, Q decomposes into its constituent elements. What is the total pressure, and what are the partial pressures of xenon and oxygen in the container?

    2. Molecular formula = XeO4

    3. I used the ideal gas law formula PV = nRT. I know that the moles (n), gas constant (R), and volume (V) are constant, so I can solve for the new pressure using the equation P1/T1= P2/T2. Rearranging to solve for P2 = 0.313 atm

    Apparently 0.313 atm is the partial pressure for Xenon and 0.626 atm is the partial pressure for oxygen. I know that when the temperature is increased that the compound breaks into its constituent elements (i.e. Xe and 2O2) but what I do not understand is why would the equation I used to solve for pressure give me the partial pressure of xenon? I thought that 0.313 atm would be the total pressure of both gases in the vessel?
  2. jcsd
  3. Aug 13, 2014 #2
    How did the total number of moles of gas in the vessel change when the compound decomposed? How many moles of X were formed, and how many moles of O2 were formed?

  4. Aug 13, 2014 #3
    Oh, so two moles of O2 were formed and 1 mole of Xe were formed. So i just needed to multiply the amount of moles by 2 to solve for O2. Thanks!
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