Explain method to determine size of molecule of oleic acid.

Explanation

Oleic acid is a liquid like soap size of its molecular is of the order of `10^(-9) m`.
In this method thickness of layer of molecular is determined. By using this dimension of molecule is determined.
`1 cm^(3)` oleic acid is mixed with `20 cm^(3)` alcohol. This is again mixed with 20 cm alcohol.
Hence concentration of oleic acid per cm will be `((1)/(20xx20)) cm^(3)`
This liquid is stored in a broad vessel and lycopodium powder is sprayed on it. A layer is formed on water surface.
When oleic acid drop is made on surface it expand uniformly in circular shape and layer of one molecule is formed on it.
To determine area (A) of layer of oleic acid diameter of layer is measured.
Let n drop of oleic acid are formed on liquid (water) surface.
Let volume of each drop `=V cm^(3)`
`:.` Total volume of n drop = nV
Volume of oleci acid in solution
=nV `xx` concentration
`=nvxx((1)/(20xx20)) cm^(3)`
Let thickness of layer of oleic acid solution on water surface be t and area of layer be A then,
`t=("volume of thin layer")/("area of layer")`
`=(nV)/(20x20xxA) cm`
If layer formed is one molecular layer then thickness t represent dimension of one molecule of oleic acid.
Dimension (thickness) of oleic acid is of the order of `10^(-9) m`