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(simple?) question on number of molecules in an area

  1. Apr 15, 2015 #1
    1. The problem statement, all variables and given/known data

    2. Relevant equations
    Please see below.

    3. The attempt at a solution


    I'm probably being really stupid here but how can the number of molecules equal


    If we integrate we get a volume multiplied by density, how can that equal a number of particles?
  2. jcsd
  3. Apr 15, 2015 #2


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    ##\rho## is not a mass density (kg/m3) but a particle density (number of particles/m3).
  4. Apr 15, 2015 #3
    Of course! many thanks for clearing this up.
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