Theme 3- . LABORATORY METHOD FOR THE DETERMINATION OF THE SIZES OF THE MOLECULES OF OLEIC ACID Flashcards
The steps
1) A solution of oleic acid in alcohol with a concentration of 0.5% is used.
2) The volume V1 of one drop can be found. For this purpose, the number of drops contained in 1 cm3 is counted, then;
V1= 1/n
3) The volume V of the monolayer can be found when 1 drop is dropped on the water surface;
V= 0.5V1/100
4) To determine the length of one molecule L of oleic acid, a small amount of talcum powder is sprinkled on the water surface and evenly distributed over the entire water surface.
When the solvent evaporates, a monolayer is formed on the surface of the water,
approximately in the shape of a circle. The average value of the diameter D is
measured and the length L is calculated according to the expression;
V= LxS , S=pi x D^2/4
5) The obtained result of the length L from the previous task is used for the determination
of the cross-section q of one molecule of oleic acid by the expression. The molar
mass of the molecule of oleic acid is M=282.5 x 10-3 kg/mol and the density p = 895 kg/m3, the number of Avogadro is NA=6.02 x 10^23 mol -1
6) The diameter d of the molecule of oleic acid can be found by the expression if
the value of cross section q is substituted.
