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Homework Help: Effusion of Gas from a Balloon

  1. Dec 8, 2009 #1
    1. The problem statement, all variables and given/known data

    Suppose we make a circular hole 2 millimeter in diameter in a balloon. Calculate the initial rate at which oxygen escapes through the hole (at 0° C), in number of oxygen atoms leaving the balloon per second.

    2. Relevant equations

    1/4 n*A*v

    3. The attempt at a solution

    1/4 n*A*v

    n = N/V at # of molecules/m^3 (density)
    n = 6.022e23/.0224 = 2.68839286E25
    This is at STP so 22.4 L volume at one mol of gas

    A = area
    Pi*.0002^2*1/4 = 3.14159265 × 10-8

    V = velocity
    = sqrt(3*k*T/m)
    k = boltzman constant 1.4e-23
    T = 273K at STP
    m = 2.65780731e-26 kg for one molecule of hydrogen

    Atoms/second = 656.816755

    What am I doing wrong?
  2. jcsd
  3. Dec 8, 2009 #2
    Re: Effusion/Gas

    Area is of the order of 10^(-6) and not 10^(-8).
    Radius, R=1mm=10^(-3)m
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