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

2. How do we show this? l 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 l Van der Waals Equation: P = RT/(V m - b) - a/V 2 m excluded attractive volume forces l Redlich-Kwong Equation: P = RT/(V m - B) - A/[T ½ V m (V m + B)] a, b, A, B depend upon type of gas

4. Van der Waals Constants

5. A Real Gas: CO 2 (experim.)

6. Van der Waals(a) & Redlich-Kwong(b): CO 2

7. Reduced Variables: T red = T/T crit

8. VdW in Critical terms

9. Reduced Eq. Of State

10. Van der Waals & Reduced Variables

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

12. Principle of Corresponding States

13. Virial Eq. Of State and Data Fitting l Z = PV m /RT = 1 + B 2V (T)/Vm + B 3V (T)/V 2 m + … B 2V (T) = 2nd virial coefficient l Z = PV m /RT = 1 + B 2P (T)P + B 3P (T)P 2 + … B 2V (T) = RT B 2P (T)

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

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

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