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Unformatted text preview: Lecture 3 1 Virial Coefficients (16.5) Recall from the past two lectures: Compressibility Factor PV Z RT = = ( 29 For 1 , Z<1 at a given pressure, suggests a significant drop in V from 'ideal' behavior. c R T T T ≈ ≈ 1 Expand Z as a polynomial in ( ): V ρ ( 29 ( 29 2 3 2 1 ... V V B T B T PV Z RT V V = = + + + This is the Virial Equation (virial  Latin for force). It was introduced in 1901 by KamerlinghOnnes for real gases. Notes : 1) Coefficients B 2V (T), B 3V (T) only depend on temperature for a given gas, not pressure. 2) B 2V (T)=B, B 3V (T)=C in other texts 2 nd virial coeff. 3 rd virial coeff. Lecture 3 2 ( 29 ( 29 2 3 2 1 ... V V B T B T PV Z RT V V = = + + + Notes cont. ( 29 2v 3) results from 2body interactions, i.e interactions involving 2 atoms/molecules. B T V ( 29 3v 2 4) comes from 3body interactions B T V ( 29 2v 5) 0, Boyle temperature B B B T T = = This is where attractive and repulsive forces cancel and the gas behaves ‘ideally’ over an extended range in pressure....
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 Spring '08
 JamesLis
 Physical chemistry, Thermodynamics, pH, Virial coefficient, b2v, virial coeff

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