CHEM 3615H CHAP 20

Assume that there is no heat exchanged with the

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Unformatted text preview: liquids is a process that can be modeled using Fick’s laws. The diffusion coefficient, D, relates the mean- square displacement, <r2> , of particles to the diffusion time, t, by: <r2> = 2 Dt Note the units of diffusion coefficient are m2.s- 1. In the special case of particles or molecules diffusing in solution, a very important equation, which characterizes the diffusion coefficient is the Einstein equation: D = kT / ζ where ζ is the friction coefficient. The friction coefficient is the proportionality constant between the friction or drag force, Fvis, and the velocity of the molecule/particle relative to that of the viscous solvent, i.e. ζ = F / v According to the Stokes law, the friction coefficient, ζ, can be written as: ζ = 6πηa where η is the solvent/medium viscosity and...
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This note was uploaded on 01/26/2014 for the course CHEM 3615 taught by Professor Aresker during the Spring '07 term at Virginia Tech.

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