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Abstract
:
In this experiment we studied the molecular diffusion in gases.
D
ab values
were gotten
experimentally
and theoretically by the use of two different
equations. In the experiment the liquid level of each tube was measured at
different times for
4 different components using a traveling microscope.
D
ab
value for Acetone, Chloroform, Hexane and Methanol were found to
be .138,
. 0665, .08387 and .0315 cm^2/s respectively. The percentage
of
errors in the experiment ranged from a high of 82.6 to a low of 2.25%.
1
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View Full DocumentIntroduction :
The diffusion coefficient depends upon the pressure, temperature and the
composition of the system. As one might expect when considering the mobility of
molecules, the diffusion coefficient are generally higher for gases than liquids and
that of liquids are higher than solids. The diffusion coefficient for the gas may be
experimentally measured in a tube. This tube, which is partially filled with pure
liquid( A ),is maintained at a constant temperature and pressure. Gas ( B ), which
flows across the open end of the tube, has a negligible solubility in liquid ( A ) and
is also chemically inert to ( A ). Component ( A ) vaporizes and diffuses into the
gas phase. The rate of vaporization may be measured and may also be
mathematically expressed in terms of the molar mass flux.
Theoretical Background :
Constant pressure and temperature, constant diffusion coefficient, one
dimensional diffusion are the usual assumptions in the theory of diffusion in an
evaporationtube.
The fundamental diffusion equation is
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 Fall '09
 M.Elgaily
 Mole

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