Experiments - 4

In the chemical laboratory we observed a model to represent a possible distribution of molecules in a container.
To understand the disposition of molecules we used many little ball of lead.

The volume of particles was of 8 cubic mm, the number of particles was 1000 and their weight was of 53,00 g. We built a monomolecular layer in a large tank and than plurimolecular layers in a graduate cylinder.

After we discussed our experiment: we had to make a monomolecular layer of a substance, and then we had to calculate the number of molecules.

We have put water in a small tank and we have waited for that it was completely firm in order to avoid that the spot, that must have a monomolecular layer, endured then distortion.

On the surface we put lycopodium powder so that the spot could be visible. The substance to use was a solution composed from oleic acid and hexan and the volume of spot had to be 0,00001 cubic cm.

This solution removes the lycopodium powder and the Asian evaporates to contact with the water only leaving oleic acid.

We have made three tests measuring the diameter of the three circular spots and then in our class everyone has found the mean of diameters and the radius. To find the area of the spot we have made radius (square) and the result multiplied for 3,14.

Then we have found the area mean adding the area of everyone and dividing the result for 8 approximating.

Since in the volume of 0,1 cubic cm there is oleic acid and Asian we have to find the volume of single oleic acid. We knew the concentration of the solution: one oleic acid part every 10000 parts of Asian. The oleic acid volume in the drop is of 0,000001 cubic cm. How many is the weight this volume? We used the density, that is the proportion between the weight and the volume in every substances. The oleic acid density is 0.873 g/cubic cm. The weight of our spot was 0.00000873 g.

How many oleic acid molecules are in this monomolecular layer?

To find this we have made reference the rule of Avogadro: every molecule has its peso;e a weight correspondent to 6,023 x 1023, 282 g of oleic acid corresponds to the number of Avogadro. The weight of the spot is therefore 0,00000873 g and the molecules are 0,00000873. In order to find the weight of a molecule we have divided to the weight of one molecule for 46,8 multiplying for (1/10) 23.

Every molecule has its weight, and 282 g of oleic acid are equivalent to Avogadro's number:

We could know the number of molecules of this layer; there are 20000000000000000 molecules!!!

In Avogadro's number there are 600000000000000000000000 molecules, 30000 times more!!!

The cartoons of experiment