Question

describe a method for measuring the molecular size of oleic acid

Answer 1

1. First we dissolve 1 cm^3 of oleic acid in alcohol to make a solution of 20cm^3.

2. We take 1 cm^3 of this solution and dilute it to 20 cm^3 using alcohol.
now the concentration equals
1/(20*20)cm^3.

3. We sprinkle lypocodium powder on the surface of water in a large trough (container) and we put one drop of this solution in uh water. This solution spreads very fast on the surface of water and forms a very thin layer of thickness t.
Suppose we have dropped n drops of water. Each drop volume = V cm^3
=n V cm^3
amount of oleic acid in this :
n V (1/20*20) cm^3
If this spreads to form a film of area A cm^3
t = volume of film / area of film
t = n V / (20*20 A) cm

Then we assume that the film has mono-molecular thickness. This becomes the size or diameter of a molecule of oleic acid.
Comes out to be 10^-9 m.

Answer 2

Answer:

• The drop quickly spreads into a thin, large circular film of a molecular thickness.
• This is the oleic acid molecules standing on their hydrophilic ends. We can measure the diameter of this circle using which we can calculate