How do you do this chemistry problem?

Question

Fatty acids spread spontaneously on water to form a monomolecular film. A benzene solution containing 0.10 mm cubed of stearic acid is dropped into a tray full of water. The acid is insoluble in water, but spreads on the surface to form a continuous film covering an area of 400. cm squared after all of the benzene has evaporated. What is the average film thickness in (a) nanometers and (b) angstroms?

Answer 1

0.1mm^3= 10^-4cm^3

the height= V/area= 10^-4/400=2.5*10^-7cm

1nm = 10^-7cm

so thickness = 2.5nm=25 angstrom

since 1 nm =10 angstroms

Answer 2

First convert 0.10 mm cube into cm.

  0.1 mm X 0.1 mm/cm X 0.1 mm/cm X 0.1 mm/cm = 0.0001cm^3

The area is 400 cm so the heigh has to be 0.0001 cm^3/400 cm=

0.000001 / 4 = 0.00000025 cm or 2.5 X 10^-7 cm. then just convert cm to nanometers and angstroms- thought I'd leave you with something to do. :)