Chapter 12: Solutions and other complex forces

2. Chapter 12: Solutions and other complex forces • 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

3. What we’ll cover: • Definitions • Control of Solubility • Things that affect solubility • Concentration units • Colligative properties

4. 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 unsaturatedIf the max or more than the max has been added, solution is saturatedCan 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)

5. 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 ºCEthanol: infinitely soluble in waterGases are infinitely soluble in one another

6. Trends and Control of Solubility For now, we are examining molecular compounds- not ionic compounds. 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? CH3OH CH3CH3 NH3

7. HydrophilicHydrophobic

8. Which of these will not dissolve in water? • NH3 • CH3CH3 • CH3OH

9. Which of these is least soluble in water? • CH3OH • CH3CH2CH2OH • CH3CH2CH2CH2OH

10. 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.

11. 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.

12. Effects of Polarity

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

15. Why do Proteins Fold?

16. Without lipids, you’d fall apart.

17. Lab calculations

18. Lab calculations

19. Nonionic Interactions: Hydrophilic vs. Hydrophobic

20. Hydrophilic vs. Hydrophobic and Ice Cream

21. What holds DNA together?

22. DNA, H-Bonding, and Entropy

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

24. Common Addition Polymers

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

26. Polar Whites!

27. Laundry!

30. Rain X

31. Control of Solubility of Ionic Compounds

32. NH4NO3 dissolution is: • Enthalpy favored • Entropy favored • Favored by both • Can’t tell for sure

33. CaCl2 dissolution is: • Enthalpy favored • Entropy favored • Favored by both • Can’t tell for sure

34. Conclusions:

36. 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?

37. Will solubility increase or decrease with increasing temperature? • Yes • No • Depends on the solute and solvent

38. Will solubility of a gas increase or decrease with increasing pressure? • Yes • No • Depends on the gas and the solvent