Question

calculate the thickness of oleic acid dropllet.​

Answer 1

Explanation:

1/20×20 cm3........................

Answer 2

Answer :

Calculating the length of very small distances like size of a molecule

Here, we will consider oleic acid molecule.

Oleic acid is a soapy liquid with large molecular size of the order of 10^{-9} m.

The procedure of calculating such small distances is as follows :

1. First form mono-molecular layer of oleic acid on water surface.
2. Dissolve 1 cm³ of oleic acid in alcohol to make a solution of 20 cm³.
3. Then we take 1 cm³ of this solution and dilute it to 20 cm³, using alcohol.
4. So, the concentration of the solution is equal to 1/20 x 20 cm³ of oleic acid per cm³ of solution.  
5. Next we lightly sprinkle some lycopodium powder on the surface of water and we put one drop of this solution in the water.
6. The oleic acid drop spreads into a thin, large and roughly circular film of molecular thickness on water surface. Then, we quickly measure the diameter of the thin film to get its area A.
7. Suppose we have dropped n drops in the water.  
8. Initially, we determine the approximate volume of each drop (V cm³).
9. Volume of n drops of solution = nV cm³.
10. Amount of oleic acid in this solution = nV(1/20*20)cm³.
11. This solution of oleic acid spreads very fast on the surface of water and forms a very thin layer of thickness t.
12. In this spreads to form a film of area A cm², then the thickness of the film : t =Volume of the film / Area of the film. t = [nV/20*20A] cm.
13. If we assume that the film has mono-molecular thickness, then this becomes the size or diameter of a molecule of oleic acid.
14. The value of this thickness comes out to be of the order of 10^{-9} m.