Abstract
In this experiment, a plot of t/hho Vs hho was made to get the slope s and then use it to
calculate the diffusion coefficient D
AB
experimentally.
Also, D
AB
was calculated
theoretically by using 2 empirical correlations. D
AB
was found for 4 different components.
They are Acetone, Chloroform, nHexane and Methanol. The components were put in
tubes where the liquid level was measured at a certain time interval. Values of D
AB
experimental and theoretical were compared and the % error was discussed. For example,
experimental D
AB
for acetone was 0.181 cm
2
/s and the theoretical one was 0.132 cm
2
/s
and the error was 37.1%. Finally, the report ends with a conclusion and recommendation.
Introduction
The diffusion coefficient for gases is affected by change of temperature and
pressure and composition. Diffusion coefficient values of gases are much higher than in
liquids and solids. The diffusivity of gases can be measured using evaporation tubes and
that was done in this experiment. The simple theory of diffusion coefficient method
involves the usual assumption of constant pressure and temperature, constant diffusion
coefficient, onedimensional diffusion, axial symmetry and absence of convection effects.
In addition, gas is assumed insoluble; hence the gas in the tube is stagnant. Finally steady
state condition. So that, the concentration gradient between the liquid level and the top of
the tube are constant.
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 Fall '09
 M.Elgaily
 Thermodynamics, Molecular diffusion, DAB, diffusion coefficient dab

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