The Size and Mass of an Oleic Acid Molecule

1
The Size and Mass of an Oleic Acid Molecule
2
1. Estimate the Width of the drop
3
Example Width of drop 0.03cm 3
X 10-2 cm
4
2. Volume of the drop (width of the
drop)3
5
Example (3 X 10-2cm)3 3 X 10-5cm3
6
3. Estimate the diameter of the Floating Circle
Diameter
7
Example Diameter 17cm
8
4. Calculate the Area of the Floating Circle
A pr2
( r d / 2 )
9
Example Diameter 17cm radius 17/2 8.5cm
Area p r2 3.14 X 8.5 X 8.5
226.9 2.3 X 102cm2
10
5. Divide the Volume of the drop by the area of
the circle to find the thickness of the floating
circle
The maximum size of the oleic acid molecule the
thickness of the floating film
11
Example Thickness volume/area
3 X 10-5 cm3 / 2.3 X102 cm2
1 X 10-7 cm
12
6. Since the oleic acid molecule has a height
that is ten times the width of the base of the
molecule, divide the thickness by ten to get the
width of the molecules base
7. Square the width of the base of the molecule
to find the area of the base of the molecule.
13
Example (1 x 10-7 cm) / 10 1 X 10-8 cm Area
of molecules base (1 X 10-8 cm)2
1 X 10-16 cm2
14
8. Divide the area of the floating circular film
by the area of the base of one molecule to find
the number of molecules in the drop.
15
Example (2.3 X 102cm2 ) / (1 X 10-16 cm2 )
2 X 1018 molecules
16
9. The mass of the drop volume X density
17
Example (3 X 10-5cm3) X (1 g/cm3)
3 X 10-5 g
18
10. The mass of a molecule the mass of all the
molecules in the drop divided by the number of
molecules in the drop
19
Example (3 X 10-5 g) / (2 X 1018 molecules)
2 X 10-23 g