Estimating size of molecule of Oleic acid The steps followed in determining the size of molecule are:
o Dissolve 1 cm 3 of oleic acid in alcohol to make a solution of 20 cm 3. Take 1 cm 3 of above solution and dissolve in alcohol to make a solution of 20 cm 3 Concentration of oleic acid in the solution will be( 1 /( 20x20)) cm 3. o
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Sprinkle lycopodium powder on the surface of water in a trough and put one drop of above solution. The oleic acid in the solution will spread over water in a circular molecular thick film.
Measure the diameter of the above circular film using below calculations.
If n – Number of drops of solution in water, V – Volume of each drop, t – Thickness of the film, A – Area of the film
Total volume of n drops of solution = nV cm 3 Amount of Oleic acid in this solution = nV( 1 /( 20x20)) cm 3 Thickness of the film = t = Volume of the film / Area of the film t = nV /( 20x20A) cm