1. Chapter 13: Control of Solubility Many of the forces we’ve talked about occur between ions/molecules in solutions Definition: A homogeneous mixture (only one phase) Examples: saltwater, tap water, gemstones, brass, air Made up of a solvent and a solute: Solvent: the substance present in the larger amount. Solute: the other substance Dissolving depends on attractive forces and entropy

2. What we’ll cover: Definitions Control of Solubility Things that affect solubility

3. Part 1: Definitions There is a maximum amount of any solute that will dissolve in a given solvent If less than the maximum has been added, solution is unsaturated If the max or more than the max has been added, solution is saturated Can also have Supersaturated solutions The concentration of a solution is the amount of solute that has been dissolved in a solvent. Many units of concentration: molarity (mol/L), weight % (g/g), ppm (mg/L)

4. Solubility If a solute will dissolve in a solvent, it is soluble. Some solutes have limits, some are infinitely soluble in a solvent. Sugar: 200 g in 100 mL water at 20 ºC Ethanol: infinitely soluble in water Gases are infinitely soluble in one another

5. Trends and Control of Solubility General rules: 1. polar solutes dissolve in polar solvents 2. nonpolar solutes dissolve in nonpolar solvents “Like dissolves Like” Oil and water don’t mix: is oil polar or nonpolar? You try: which of these will dissolve in water? CH 3 OH CH 3 CH 3 NH 3 For now, we are examining molecular compounds- not ionic compounds.

6. Hydrophilic Hydrophobic

7. Which of these will not dissolve in water? 1.NH 3 2.CH 3 CH 3 3.CH 3 OH

8. Which of these is least soluble in water? 1.CH 3 OH 2.CH 3 CH 2 CH 2 OH 3.CH 3 CH 2 CH 2 CH 2 OH

9. Introduction to Thermodynamic Control of the World Enthalpy,  H: Stronger bonds/IMFs are favored over weak ones. Entropy,  S: Freedom of movement is favored over constrained states.

10. Trends and Control of Solubility and Mixing: Why do some things mix and others do not? What controls Solubility: Enthalpy (enthalpy of solution) Negative if new forces are stronger than original forces Entropy Depends on the entropy change of both the water and the solute.

11. Effects of Polarity

13. Why don’t water and oil mix? 1.Enthalpy: Water wants to keep H- bonds 2.Entropy: Water won’t form constricted arrangements

14. Why do Proteins Fold?

15. Without lipids, you’d fall apart.

16. What holds DNA together?

17. DNA, H-Bonding, and Entropy

18. Introduction to Polymers Polymers are long molecules made of repeating units, called monomers. In general: Specific example:

19. Common Addition Polymers

20. Forces between polymer chains: Crosslinks Weak: Intermolecular force crosslinks Strong: Colvalent bond crosslinks

21. Polar Whites!

22. Laundry!

25. Part 2: External Control of Solubility Temperature and Pressure Predictions: Will solubility increase or decrease with increasing temperature? Will solubility of a gas increase or decrease with increasing pressure?

27. What is the solubility of O 2 in grams per liter, given normal atmospheric conditions?

28. Henry’s Law Constants: when are they constant? Which is greater, k H for O 2 at 20 o C or O 2 at 50 o C? Which is greater, k H for O 2 or k H for NH 3 ?

29. Henry’s Law, Solubility, and my Diet Coke