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Chem 300 - Ch 16/#2 Today’s To Do List

Chem 300 - Ch 16/#2 Today’s To Do List. Equations of State catchup More about the Critical State Law of Corresponding States Virial Equations Intermolecular Potentials(Intro). How do we show this?. Devise a better equation of state by: Correcting for IG deficiencies. Attractive forces

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Chem 300 - Ch 16/#2 Today’s To Do List

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  1. Chem 300 - Ch 16/#2Today’s To Do List • Equationsof State catchup • More about the Critical State • Law of Corresponding States • Virial Equations • Intermolecular Potentials(Intro)

  2. How do we show this? • Devise a better equation of state by: • Correcting for IG deficiencies. • Attractive forces • Excluded volume (repulsive) forces • Curve-fitting experimental data.

  3. Adjustments to the Ideal Gas Eq. Of State • Van der Waals Equation: • P = RT/(Vm - b) - a/V2m • excluded attractive • volume forces • Redlich-Kwong Equation: • P = RT/(Vm - B) - A/[T½Vm(Vm + B)] • a, b, A, B depend upon type of gas

  4. Van der Waals Constants

  5. A Real Gas: CO2 (experim.)

  6. Van der Waals(a) & Redlich-Kwong(b): CO2

  7. Reduced Variables: Tred = T/Tcrit

  8. VdW in Critical terms

  9. Reduced Eq. Of State

  10. Van der Waals & Reduced Variables

  11. Some Critical ConstantsP(atm), V(mL/mol), T(K)

  12. Principle of Corresponding States

  13. Virial Eq. Of Stateand Data Fitting • Z = PVm/RT = 1 + B2V(T)/Vm + B3V(T)/V2m+ … • B2V(T) = 2nd virial coefficient • Z = PVm/RT = 1 + B2P(T)P + B3P(T)P2 + … • B2V(T) = RT B2P(T)

  14. The 2nd Virial Coefficient [B(T)] • Shows deviation from gas ideality (B<0 at low T) • When attractive and repulsive forces cancel, B = 0, T = TBOYLE

  15. B(T) can tell us about the intermolecular (IM) forces affecting different gases

  16. B(T) tells us about the IM forces affecting a gas at different T

  17. Next Time • More on IM Forces • A bit on Potential Energy • Lennard-Jones & Other Potentials • What is a London Dispersion force?? • The return of Van der Waals

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