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Homework Help: Colloid science

  1. Dec 21, 2012 #1
    1. The problem statement, all variables and given/known data
    Lauric acid , CH3(CH2)10CO2H has been dispersed 500cm2+ on the water surface. Assume that the cross-sectional area of acid molecule to be 18.2A2+ and the density of the initial acid is 0.78gcm3-, calculate the amount of acid that dispersed on the surface of water.

    * the problem i face is, i don't know how to find number of moles of lauric acid...
    please some one help me...

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Dec 22, 2012 #2


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    You need to determine the minimum amount of lauric acid that will cover the surface of area 500 cm2. Each molecule has a cross sectional area of 18.2 square angstroms. Assume the lauric acid can be described by a sphere of radius √(18.2/∏) in angstroms. Find out the best packing fraction that a single layer array of spheres covering a surface would be and count them for 500 cm2.
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