CHEM 3615H CHAP 20

Expressions for the collision flux and effusion rates

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Unformatted text preview: erage speed. Consideration of the collisions between gas particles also leads to the concepts of collision diameter (the molecular diameter, d), collision cross- section (σ = πd2), mean free path, λ and collision frequency, z. It is found that the collision frequency and mean free path are expressed as: z = ((2)1/2σ <c> p )/ kT and λ = k T/σ p Consideration of collisions of molecules with walls and surfaces leads to the concept of collision flux, ZW, and allows for the estimation of the effusion rate, reff. Expressions for the collision flux and effusion rates are given by: ZW = p / (2πmkT)1/2 and reff = ZW A. Use the above expressions to understand why the mean free path does NOT depend on temperature in a vessel of constant volume but why the collision frequency and the collision flux do increase with temperature. Another very important set of concepts in this chapter relates to the Transport Properties of matter. In section 20.4, focus is placed on the...
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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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