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Please help me with some gas law problems

  1. Sep 29, 2008 #1
    1. The problem statement, all variables and given/known data

    1) Liquid helium at 4.2 K has a density of 0.147 g/mL. Suppose that a 2.50-L metal bottle that contains air at 105K and 2.0 atm pressure is sealed off. If we inject 100.0 mL of liquid helium and allow the entire system to warm to room temperature (25 °C), what is the pressure inside the bottle?

    2) A mouse is placed in a sealed chamber with air at 752.0 torr. This chamber is equipped with enough solid KOH to absorb any CO2 and H2O produced by the mouse. The gas volume in this chamber is measured to be exactly 2.30 L, and the temperature is held constant at 296K.
    After two hours the pressure inside the chamber falls to 723.2 torr. What mass of oxygen has the mouse consumed?
     
  2. jcsd
  3. Sep 30, 2008 #2

    Borek

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    Staff: Mentor

    PV=nRT

    Show what you did.
     
  4. Oct 2, 2008 #3
    For the second problem, you are going to have to know the molarity of oxygen, so that you can find the original amount of O2 (grams) in the 2.30 L of O2. After you know the grams of O2, you can figure out the "n." Then, use PV=nRT, to calculate the new "n." By subtracting the new "n" from the old "n," and converting that molar value into grams, you get your answer.
     
  5. Oct 2, 2008 #4

    Borek

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    Staff: Mentor

    Not sure what you mean by "molarity" of oxygen, but you don't have to know it. Think about stoichiometry O2 -> CO2.
     
  6. Oct 2, 2008 #5

    GCT

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    Science Advisor
    Homework Helper

    You had already posted the first problem ... what's the textbook answer?
     
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