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Homework Help: Finding Molar Mass of Unknown Gas

  1. Feb 2, 2010 #1
    Given the following data for a gas, use the equation for the ideal gas law to calculate the molar mass.

    Mass = 0.810 g
    Pressure = 0.954 atm
    Volume = 0.461 L
    Temp = 291 K



    M = mRT/PV = 44.0?
     
  2. jcsd
  3. Feb 2, 2010 #2
    I won't give you the answer but the following is how you solve the equation

    PV=nRT

    P=pressure (0.954 atm [use kpa since that is what is required in the ideal gas law thus pressure is 0.954*101.325 kpa = 96.66405 kpa])

    V=volume (0.461 L)

    R=Universal gas constant or 8.314

    T=temperature (291 K)

    m=mass (0.810 g)

    n=mol (unknown)

    M=molar mass (unknown)

    PV=nRT which becomes

    n=PV/RT

    After you get mols, use this formula n=m/M or M=n*m
     
  4. Feb 2, 2010 #3
    OK I understand now -- thank you!
     
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