Chemistry 102(01) Spring 2012

1. Chemistry 102(01) Spring 2012 CTH 328 9:30-10:45 am Instructor: Dr. UpaliSiriwardane e-mail: upali@latech.edu Office: CTH 311 Phone 257-4941 Office Hours: M,W 8:00-9:00 & 11:00-12:00 am; Tu,Th,F8:00 - 10:00 am.. Exams: 9:30-10:45 am, CTH 328. March 26 , 2012 (Test 1): Chapter 13 April 18 , 2012 (Test 2): Chapter 14 &15 May 14 , 2012 (Test 3):Chapter 16 &18 Optional Comprehensive Final Exam: May 17, 2012 : Chapters 13, 14, 15, 16, 17, and 18

2. Chapter 15. The Chemistry of Solutes and Solutions 15.1 Solubility and Intermolecular Forces 15.2 Enthalpy, Entropy, and Dissolving Solids 15.3 Solubility and Equilibrium 15.4 Temperature and Solubility 15.5 Pressure and Dissolving Gases in Liquids: Henry's Law 15.6 Solution Concentration: Keeping Track of Units 15.7 Vapor Pressures, Boiling Points, and Freezing Points of Solutions 15.8 Osmotic Pressure of Solutions 15.9 Colloids 15.10 Surfactants 15.11 Water: Natural, Clean, and Otherwise

3. Solution Terminology Solute • one or more substance(s) dispersed in the solution Solvent • majority substance in a solution The solubility of a solid in a solvent is typically given in g/100 ml. Types of solutions • Mixture of Gases • Liquid solutions (L+S,L+L,L+G) • Solid solutions (S+S, alloys) • Aerosols (L+G) • Foam (S+G)

4. Miscible vs. Immiscible

5. “Likes Dissolve Likes” • Materials with similar polarity are soluble in each other. Dissimilar ones are not. • Polar substances with similar forces are likely to be soluble in each other • Non-polar solutes dissolve in non-polar solvents • stronger solute-solvent attractions favor solubility, stronger solute-solute or solvent-solvent attractions reduce solubility

6. Solubility of Ionic Compounds and Temperature

7. Solution Terminology Miscible - liquids that dissolve in each other Immiscible - liquids that do not dissolve in each other due to differences types of interactions Saturated solution A solution that contains as much it can hold Unsaturated solution A solution that contains less than maximum amount Supersaturated solution A solution that contains more than maximum amount

8. Types of Solutions (Diluted, Saturated, and Supersaturated)

9. Supersaturated Solution

10. Solute - Solvent Interactions

11. The Solution Making Exopthermic Process

12. The Solution Making Endothermic Process

13. Thermodynamic Factors Affecting Solubility Energy: Enthalpy (DH) Lowerenergy – DH 2. Order: Entropy (DS) Disorder + DS Exothermic –DH favorssolubility: productfavored Mixing (+DS disorderfavorssolubility:productfavored Gibbs Free Energy: (Chapter 18) DGsoln= DHsoln -TDSsoln,

14. Types of Solute - Solvent Interactions All interactions are electrostatic force ~ Coulombic: proprotional to charge and séparation) London Dispersion Forces: (O2dissolved in Liq. N2) Ion-Ion Interaction: (Ionic liquids in batteries) Ion-Dipole Interaction (hydrated ions Na+(aq)) Dipole-Dipole Interaction (CCl4 in benzene (C6H6) HydrogenBonding. (water and éthanol)

15. 1) What are the main factors affecting a solubility of a solute in a solvent?

16. The Solution Making Exopthermic Process

17. The Solution Making Endothermic Process

18. 2) Arrange the following inter-particles forces in liquids and solids in the order of increasing strength: • ion-ion, • ion-dipole, • hydrogen bond, • dipole-dipole and • London dispersion

19. 3) Identify the most important type of inter-particle force for each of the following compounds: • NaCl(s) or NaCl(l) b) N2(l) or N2(s) • N2(g) d) Na(s) and Na(l) • e) H2O(l) or H2O(s) f) CH3CH2OH(l) or CH3CH2OH(s)

20. 4) Which of the above inter-particle force could be named as intermolecular force? • NaCl(s) or NaCl(l) b) N2(l) or N2(s) • N2(g) d) Na(s) and Na(l) • e) H2O(l) or H2O(s) f) CH3CH2OH(l) or CH3CH2OH(s)

21. Identify Hydrogen Bonding, Polar and Non-polar groups in Covalent Molecules Acetic acid HC2H3O2 CH3COOH Hexanol C6H13OH Propanoic acid C2H5COOH Hexane C6H14 “Like Dissolves Like”

22. 5) What types of inter-particle forces • solute-solute:DH1, • solvent-solvent: DH2, • solvent-solute:DH3) are involved when • CH3CH2OH(l): dissolved in water,H2O: • DH1= ; DH2= ; DH3= • For covalent compounds: DHsoln= DH1+ DH2+ DH3

23. Water Dissolving An Ionic Solute

24. Solution Process of Ionic Compounds

25. Hydration of a Sodium Ion

26. Heats of Solution

27. 4) b)Na2SO4(s)dissolved in water: • DH1 = ; DH2 = ; DH3 = • Ion-ion inter-particle forces in solids are called Lattice Energy. ( this is related to DH1) • Ion-water inter-particle forces are called Hydration Energy (this is related to DH2 and DH3) • For ionic compounds; DHsoln= DHlattice+ DHhyd • Qualitatively speaking which of the above a) or b) would have a more exothermic DHsoln?

28. 4) What factors make it more exothermic? • CH3CH2OH in H2O • DH1 = ; DH2 = ; DH3= • Na2SO4(s)dissolved in water: • (DH1= DHsoln)+ (Hhyd=DH2+ DH3)

29. 5) Assign the entropy (most +, medium + or least +) for i) S1 –solute: ii) S2-solvent: iii) S3, solution (solvent-solute): • For the following: (Indicate which one is highest, intermediate and lowest order) For • a) CH3CH2OH(l): dissolved in water: • S1 = ; S2 = ;S3= • Na2SO4(s)dissolved in water: • S1 = ; S2 = ;S3 =

30. 5) Qualitatively speaking which of the above a) or b) would have a more positive DSsoln? • a) CH3CH2OH(l): dissolved in water: • S1 = ; S2 = ;S3= • For Na2SO4(s)dissolved in water: • S1 = ; S2 = ;S3 =

31. 6) Calculate the DHsolnfor dissolving CaCl2(s) in water given the Lattice-Energy CaCl2(s) = +2258 kJ/mole), and Hydration energy for CaCl2 = - 2205 kJ/mole (DHsoln = DHlattice+ DHhyd=?)

32. 7) DHsolnvalue thermodynamically product favored?

33. 8) For dissolving CaCl2(s) in water, which of the following entropy represent the highest order? Explain. • S for CaCl2(s): +104.6 J/mole b) S for H2O(l): +69.91 J/mole c) S for solution CaCl2(aq): +815 J/mole

34. 9) Calculate the DSsolnfor dissolving CaCl2(s) in water given the entropies of Lattice- CaCl2(s) (S1= +104.6 J/mole), H2O(l)(S2= +69.91 J/mole); CaCl2(aq)(S3 = +815 J/mole). • DSsoln= Sfinal-Sinitial =S3 - ( S1+ S2)?

35. 10) Calculate the DSsolnfor dissolving CaCl2(s) in water given the entropies of Lattice- CaCl2(s) (S1= +104.6 J/mole), H2O(l)(S2= +69.91 J/mole); CaCl2(aq)(S3 = +815 J/mole). • DSsoln= Sfinal-Sinitial =S3 - ( S1+ S2)?

36. 11) DSsolnvalue thermodynamically product favored?

37. 12) Based on DGsoln, determine if CaCl2 is soluble at 25C, given, • DGsoln= DHsoln-TDSsoln, • and DHsolnand DSsolncalculated above.

38. 13) Why sand is insoluble in both polar and nonpolar solvents?

39. 14) How does temperature and pressure affect the solubility of following? • NH4NO3(solid) in water with +(positive) DHsoln: • CO2 gas in water:

40. Solubility of Oxygen in Water

41. Henry’s Law

42. Henry’s LawSolubility of Gases in Solvents Sg = kHPg where Sg solubility kH Henry’s Law constant Pg partial pressure of gas Increasingthe pressure of a gas above a liquid increases its solubility

43. 15) Deep sea divers may experience a condition called the "bends" if they do not readjust slowly to the lower pressure at the surface. Using the diagram on pressure dependence solubility of gases on water explain this phenomenon.