Calculating the Amount of Lauric Acid Dispersed on Water Surface

[kimia786]

Homework Statement

Lauric acid , CH3(CH2)10CO2H has been dispersed 500cm2+ on the water surface. Assume that the cross-sectional area of acid molecule to be 18.2A2+ and the density of the initial acid is 0.78gcm3-, calculate the amount of acid that dispersed on the surface of water.

* the problem i face is, i don't know how to find number of moles of lauric acid...
please some one help me...

Homework Equations

The Attempt at a Solution

 

[chemisttree]

You need to determine the minimum amount of lauric acid that will cover the surface of area 500 cm². Each molecule has a cross sectional area of 18.2 square angstroms. Assume the lauric acid can be described by a sphere of radius √(18.2/∏) in angstroms. Find out the best packing fraction that a single layer array of spheres covering a surface would be and count them for 500 cm².