 # In an experiment to estimate the size `
Question:

In an experiment to estimate the size of a molecule of oleic acid, 1mL of oleic acid is dissolved in 19mL of alcohol. Then 1mL of this solution is diluted to 20mL by adding alcohol. Now, 1 drop of this diluted solution is placed on water in a shallow trough. The solution spreads over the surface of water forming one molecule thick layer. Now, lycopodium powder is sprinkled evenly over the film we can calculate the thickness of the film which will give us the size of oleic acid molecule.

(a) Why do we dissolve oleic acid in alcohol?

(b) What is the role of lycopodium powder?

(c) What would be the volume of oleic acid in each mL of solution prepared?

(d) How will you calculate the volume of n drops of this solution of oleic.

(e) What will be the volume of oleic acid in one drop of this solution?

Solution:

(a) Oleic is dissolved in the alcohol because it does not get dissolved in water.

(b) With the help of lycopodium powder one can measure the area over which the oleic acid spreads as lycopodium powder clears the circular area when oleic acid is added.

(c) 20mL of oleic acid contains 1mL of oleic acid.

This means that each mL of solution contains 1/20 mL of oleic acid.

1mL of this solution is diluted to 20mL by adding alcohol.

Therefore, each mL of solution prepared, volume of oleic acid = (1/20)(1/20) = 1/400mL

(d) To calculate the volume of n drops of this solution of oleic, burette and measuring cylinder can be used.

(e) The volume of oleic acid in one drop = 1/400mL