Lab Report Gas Diffusion

3047 WordsMar 1, 201313 Pages
S5E1 Gaseous Diffusion 1.0 ABSTRACT In this experiment, our objective is to find out the gas diffusion coefficient, D of acetone in the air. This experiment is conducted at a temperature of 50ºC and atmospheric pressure. The method that is applied to conduct this experiment is called the Winkleman method where the level of acetone (Z) is determined every 15 minutes by using a microscope. With the level of acetone being determined, a graph of t/L+Lo (min /mm) vs. L-Lo (mm) is plotted and the gradient s of the graph is being calculated. With the gradient of the graph s, we calculated the diffusion coefficient, D of the experiment by applying Fick’s Law with mathematical derivation. From the experiment, the diffusion coefficient, D is…show more content…
If a surface is introduced on which A is absorbed but B is not absorbed, a partial pressure gradient will be set up, causing A to diffuse towards and B away from the surface. Given this process to continue for a short interval, A will be absorbed at the surface and B will tend to diffuse away. Thus a total pressure gradient will be produced causing a bulk motion of A and B towards the surface, in addition to the transfer by diffusion. Since there is no net motion of B, the bulk rate or flow must exactly balance its transfer by diffusion. Thus the bulk rate of flow of B = – NB = [pic] The bulk flow of B is accompanied by a bulk flow of A as below: Bulk flow of A = [pic] = [pic](9) The total rate of transfer of A is obtained by summing the transfers by diffusion and bulk flow. By adding equation (5) and (9), the total transfer, NA’ is given by: NA’ = [pic](5) + (9) NA’ = [pic] (10) This relation shown by equation (10) is known as Stefan Law. Integration of equation (10) between two positions denoted by suffixes 1 and 2 gives us the results as below: [pic] NA’ = [pic] (11) NA’= [pic] NA’=[pic] (12) NA’=[pic] (13) where the suffix m denotes the logarithmic mean value of the
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