2. Previously in Chem 104: Solutions: macroscopic & microscopic Deducing Enthalpies of Solution Energetics (Enthalpies) of Dissolution— they can be exo- and endothermic TODAY QUIZ answer key out - send self-check by Tuesday midnight Another BIG IDEA- Equilibrium Effects on Dissolution by:  P  T Effects of Dissolution on: vapor pressure boiling freezing

3. A really BIG IDEA in chemistry

4. Closely followed by

5. We need another word to pair with Dynamic As applied to a solid in equilibrium with a solvent in solution:

6. Combined with Example 1. This explains phase changes in phase diagrams “ a system at equilibrium when disturbed will adjust to remove or minimize the effect of the disturbance”

7. H 2 O Phase Diagram Temperature, deg C Pressure, atm solidliquid gas 0 deg 1 atm icewater

8. H 2 O Phase Diagram Temperature, deg C Pressure, atm solidliquid gas 0 deg 1 atm ice make more water 5 atm melts lower T

9. Combined with This explains almost all Solution behaviors Example 2. How gas pressure affects solubility S g = k h P g Gas solubility depends on gas partial pressure S g = k h P g Henry’s Law Constant

10. A related example: How temperature affects gas solubility Increase T and: Combined with Explains almost all Solution behaviors Gas + solvent Gas solution + energy (exothermic) Gas + solvent Gas solution + energy

11. Another related example: How temperature affects solid solubility Increase T and: Combined with Explains almost all Solution behaviors Case A. MX + water M- (aq) + X- (aq) + energy MX + water M- (aq) + X- (aq) + energy Less dissolves Increase T and: Case B. MX + water + energy M- (aq) + X- (aq) MX + water + energyM- (aq) + X- (aq) More dissolves

12. Combined with Explains almost all Solution behaviors Example 3. How a solute affects solvent vapor pressure P solvent = X solvent P o solvent

13. Combined with Explains almost all Solution behaviors Example 3. How a solute affects gas pressure  P solvent = - X solute P o solvent

14. Combined with Explains almost all Solution behaviors Example 4. How a solute affects solvent boiling point  T bp = K bp m solute When does a liquid boil? Lower vapor pressure, requires more energy, higher T, to get to atmospheric pressure: Boiling Point Elevation What changes if we add a solute? Ebullioscopic constant  T bp = K bp m solute

15. Combined with Explains almost all Solution behaviors By extension: How a solute affects solvent freezing point  T fp = K fp m solute

16. Combined with Explains almost all Solution behaviors Three examples of Colligative Properties: colligative – depends only on the number of particles  T fp = K fp m solute  T bp = K bp m solute  P solv = X solvent P o solvent  T fp = K fp m solute  T bp = K bp m solute  P solv = X solvent P o solvent

17. Calculations based on Colligative Properties: requires different concentration units M, molarity = #moles solute / liter solvent m, molality = #moles solute / kg solvent Weight % = (mass A/ total mass) x 100% Mole fraction= #moles A / total # moles We need to deal with concentration expressed as mole fraction, molality because collogative properties deal only with number of particles in solution, not identities.