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Homework Help: Help calculating a diffusion rate using Fick's equation.

  1. Feb 19, 2012 #1


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    1. The problem statement, all variables and given/known data

    Organism weight = 25 g
    Organism lenght = 30 cm
    [Na+ (ECF)] = 200 mM
    [Na+ (water)] = 500 mM
    ΔX(gill) = 6 μm
    ΔX(skin) = 25 μm
    A(gill) = 5.0 cm^2/gm
    A(skin) = 10 cm^2/gm
    Dk(gill) = 2 X 10^4 cm^2/s
    Dk(skin) = 1 X 10^4 cm^2/s

    Calculate the Na+ rate of diffusion through the skin using Fick's equation: (Dk)(A)((C1-C2)/dX)

    2. Relevant equations

    Fick's equation: (Dk)(A)((C1-C2)/dX)

    3. The attempt at a solution

    I'm not sure too sure if the answer that I'm getting is right. It seems to be too high and the units seem confusing.

    Rate = (1 X 10^4)(10)((500-200)/25*10000) = 120 cm^3*mM/s*gm.

    I am not sure if I should also use the weight and the length of the organism.

  2. jcsd
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