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Homework Help: Simple RMS velocity question, what's wrong with my answer?

  1. Mar 24, 2017 #1
    • Thread moved from the technical forums, so no Homework Template is shown
    Find the rms speed for an argon atom if 1.5 mol of the gas is confined to a 5.6 liter container at a pressure of 5.5 atm.

    PV = nRT
    RT = PV/n
    v_RMS = \sqrt (3RT/M)

    = \sqrt (3PV/nM)

    = \sqrt ((3 * (5.5atm * 101.325kPA/atm) * (5.6 * 10^-3 m^3) / (1.5 mol * 39.948 * 10^-3)

    = 12.5 m/s

    However this is apparently wrong. Can someone please tell me what I went wrong?

  2. jcsd
  3. Mar 24, 2017 #2

    Philip Wood

    User Avatar
    Gold Member

    Your substitutions are correct, but you've slipped a factor of 1000 (possibly the k in kPa) in your working out. This becomes a factor of sqrt (1000).
  4. Mar 24, 2017 #3
    Thank you!
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