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Homework Help: Velocity of Gases

  1. Dec 3, 2005 #1
    Which of the following gases has the lowest average speed at 25C?
    Is it H2S? Given the formula sqrt(3RT/M), is it not true that the gas with the greatest molar mass will have the lowest speed?
    NH3 = 17.03 g/mol
    O2 = 32 g/mol
    H2S = 34.08 g/mol
    CH4 = 16.04 g/mol
  2. jcsd
  3. Dec 3, 2005 #2


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    Homework Helper

    Yes, the KE of each molecule (at the same Temperature) is the same.
    KE = ½ m v^2 = 3/2 k_B T
    If you haven't seen it yet, k_B = k_Boltzmann = R/N_Avagadro
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