2. Physical Chemistry Dónal Leech donal.leech@nuigalway.ie Ext 3563 Room C205, Physical Chemistry Notes for downloading (powerpoint and word) http://www.nuigalway.ie/chem/Donal/Teaching.htm

3. Chemistry Biological Sciences  Organisms  Organs  Tissues  Cells  DNA Physical Sciences  Sub-atomic  Atoms  Materials  Atmosphere  Stellar Chemistry Molecular Sciences  Molecules  Bonds  Forces

4. Physical Chemistry Establishes and develops the principles that are used to explain and interpret the observations made in chemistry Bulk  Individual  Rates Equilibrium  Structure  Change Thermodynamics   Chemical reactions Quantum mechanics & spectroscopy ENERGY

5. Textbook Brown, LeMay, Bursten Chemistry: The Central Science, 9 th Edition Companion Web-site http://www.prenhall.com/brown

6. Dynamic Equilibrium Chapter 15 Example liquid + heat  vapour an endothermic physical change

7. Le Chatelier’s Principle When a dynamic equilibrium is upset by a disturbance, the system responds in a direction that tends to counteract the disturbance and, if possible, restore equilibrium liquid + heat  vapour Increase the temperature (add heat)

8. Le Chatelier’s Principle When a dynamic equilibrium is upset by a disturbance, the system responds in a direction that tends to counteract the disturbance and, if possible, restore equilibrium liquid + heat  vapour Liquid evapourates to absorb the added heat and the position of the equilibrium shifts to the right

9. Solution of a Weak Acid CH 3 COOH + H 2 O  H 3 O + +CH 3 COO - For a given composition of a system, equilibrium is independent of which side you approach it from…..reactions are REVERSIBLE N 2 O 4 (g)  2NO 2 (g) C init 0.0350 mol0 or00.0700 mol C equil 0.0292 mol0.0116 mol

10. Equilibrium Law simple relationship between molar concentrations (or pressures) of reactants and products at equilibrium H 2 (g)+I 2 (g)  2HI(g) (at 440C) Mass action expression: Where Q is the reaction quotient LAW:at equilibrium the reaction quotient is equal to the equilibrium constant, K. In general for dD + eE  gG + hH

11. Heterogeneous Equilibria (involving more than one phase)

12. Equilibrium Law for Gaseous Reactions For gaseous reactions use partial pressures, P, to give an equilibrium constant (K p )

13. Predicting direction of equilibrium changes (Le Chatelier redux) Adding or removing reactant or product Cu(H 2 O) 4 2+ (aq.) + 4Cl - (aq.)  CuCl 4 2- (aq.) + 4H 2 O Changing volume (or pressure)-gases only as liquids and solids are incompressible Decrease V=>increase P System opposes this by reducing the number of molecules

14. Predicting direction of equilibrium changes (Le Chatelier redux) Changing temperature (heat) System opposes this by trying to absorb the added heat ONLY factor that actually changes the value of K Effect of catalyst Speeds up approach to equilibrium, but does not alter K or the system (kinetics)