Ch. 16  Solutions

1. Ch. 16 Solutions

2. Solutions are homogeneous mixtures that may be solid, liquid or gas.

3. Alloy

4. Formation of a solution • The composition of the solute and solvent will determine whether a substance will dissolve.

6. Stirring (agitation), temperature, and the surface area of the solutes determine how fast the substance will dissolve.

7. Surface area

9. Temperature

11. Stirring

12. Solubility How well a solute can dissolve in a solvent. • Saturated solution Contains the maximum amount of solute possible for a given temperature and pressure.

14. Unsaturated Solution More solute can be squeezed into the solution. • Miscible Two liquids can be mixed • Immiscible Two liquids that don’t mix.

16. Temp affects the solubility of solid, liquids and gases. Both Temp and Pressure affect the solubility of gases.

17. Supersaturated solution Contains more solute than allowed at that temperature.

18. Seed Crystal

19. Solubility for gases S1/P1 = S2/P2 Unit of solubility is g/L, pressure is atm

20. How well does gas dissolve?

21. Concentration Molarity mols/Liter

22. If there are 5 mols of NaCl in 20 liters of water, what is molarity of the NaCl solution? • .25 M

23. Making Dilutions M1*V1 = M2 * V2

24. You have a 1 M NaCl solution. How can you make 10 Liters of a .5 M solution? • Use 5 liters of 1M solution, then fill to 10 L with water.

25. How can you make 10 L of .2 M NaCl by using 2 M NaCl?

26. Percent concentration volume/volume • Volume solute/ total volume * 100%

27. Percent concentration (mass/mass) Mass solute/mass solution * 100%

28. What is the Molarity of a .9 g / 100 mL solution of NaCl (58.5 = molar mass)? • .15 M

29. NOTES 2 • Colligative Properties: Depend only on the number of solute particles.

30. Vapor-pressure lowering: Solutes will lower the vapor pressure. • Solute molecules “trap” solvent molecules. This makes it more difficult for the solvent molecules to evaporate.

32. Draw this • What will produce the greatest lowering in vapor pressure, 3 mols of glucose, 3 mols of NaCl, or 3 mols of CaCl2?

33. Freezing point depression The more solutes in a solution, the lower its freezing/melting point.

34. The more solute molecules a solution has, the more difficult it is to compact together and freeze.

35. Which is harder to freeze?

38. Which will have the lowest freezing point? 3 M NaCl, 3 M PCl3

39. Boiling point elevation Solutes get in the way of solvent molecules and make it harder for them to evaporate away.

41. Molality (m): moles of solute / kg of solvent

42. What is the Molality? 2 mols of NaCl, 4 kg of water. • .5 molal

43. Mole Fraction • Mols of one thing divided by Total mols of everything. • What is the mol fraction of NaCl if it is in a solution that contains 2 mol NaCl, 2 mol of LiBr, and 6 mol of H2O? • .2

44. ∆Tf = Kf * m (FP depression) • Kf = Molal freezing-point depression constant • ∆Tb = Kb * m (BP Elevation) • Kb = Molal boiling-point elevation constant

45. What is the freezing point depression and the new freezing point of a solution that has 1.61 mols of C2H6O2 antifreeze in .5 kg of water? • 1.86 * 3.22 = 5.99 • -5.99 C is new freezing point

46. Partner Review Activity: • Page 499, #42, 51

47. #52, 53

48. #54, 57

49. #61, 63

50. # 76, 78