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Homework Help: Kinetic Theory of Gases and speed of oxygen molecules

  1. Apr 15, 2007 #1
    1. The problem statement, all variables and given/known data

    A syringe of volume 20 ml has just been used and now lies empty on the doctor's desk. The pressure in the office is 100,000 Pa. Assume that the air is an ideal gas consisting of nitrogen N2 (80%) and oxygen O2 (20%) molecules. k=1.38×10-23 J/K and the molar mass of oxygen is 32 g/mol.

    The syringe must be heated to high temperatures to sterilize it. When the syringe is at its maximum temperature, the number of oxygen molecules is 6.5 x 1019 (but the pressure, volume, and percent oxygen remain the same), what is the rms speed of the oxygen molecules?

    2. Relevant equations

    Kinetic theory of Gas


    3. The attempt at a solution

    m=32/6.5e19=4.9e-22kgNot sure if this is right..

    v=sq rt(3(1.38e-23)(445.93)/4.9e-22)

    so i got 6.13m/s but its wrong, can someone explain to me what i did wrong?
  2. jcsd
  3. Apr 15, 2007 #2
    figured it out, mass should of been .032Kg/6.022e23
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