1 / 25

CH 11: Properties of Solutions

CH 11: Properties of Solutions. Describing Solutions – concentration units Energetics of solution formation Factors impacting solubility – P and T Colligative Properties of solutions BP elevation FP depression Osmotic pressure Vapor Pressure. Terms. Solution – homogeneous mixture

ahanu
Télécharger la présentation

CH 11: Properties of Solutions

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. CH 11: Properties of Solutions • Describing Solutions – concentration units • Energetics of solution formation • Factors impacting solubility – P and T • Colligative Properties of solutions • BP elevation • FP depression • Osmotic pressure • Vapor Pressure

  2. Terms • Solution – homogeneous mixture • Solvent – generally the larger component of the solution • Determines the physical state of the solution • Solute – generally the smaller component of the solution • Solute is dispersed in the solvent

  3. Solution Composition • Concentrated solution – relatively large amount of solute • Dilute solution – relatively small amount of solute

  4. Solution Composition • Unsaturated solution –solution with less than the maximum amount of solute that will normally dissolve at a given temperature • Saturated solution - solution with maximum amount of solute that will normally dissolve at a given temperature

  5. Solution Composition • Super-saturated solution - solution with more than the maximum amount of solute that will normally dissolve at a given temperature

  6. Concentration Units Molarity (M) = moles solute/Liters solution Molality (m) = moles solute/kg solvent Mass % = Mass solute/mass solution x100% Mole fraction (cA) = moles A/total moles

  7. Normality Normality (N) = # gram equivalent wt./L solution • Gew = mass of an acid or base that produces 1 mole of H+ or OH -1 Normality = Molarity x (# H+ or OH -1 /mol) • 1 M HCl = 1 N HCl • 1 M H2SO4 = 2 N H2SO4 For acid base titrations: (NAcid) (VAcid) = (NBase) (VBase)

  8. Practice! • Start by writing definitions for the concentration units M = m = Mass % = Mole fraction =

  9. Starting with Molarity Solution: • 3.75 M H2SO4 solution with a density of 1.23 g/mL Calculate: • Mass % • Molality • mole fraction of H2SO4

  10. Starting with Masses Solution: • A solution is made by combining 66.0 grams of acetone (C3H6 O) with 146.0 grams of water. • Solution has a density of 0.926 g/mL Calculate: • Molarity – need volume of solution • Mass % • Molality • Mole fraction of acetone

  11. Starting with Mass % Solution: • 35.4 % H3PO4 • Density of 1.20 g/mL Calculate: • Molarity • Molality • Mole fraction of H3PO4

  12. Starting with Molality Solution: • 2.50 m HClsolution • Density of 1.15 g/mL Calculate: • Molarity – need _______ • Mass % • Mole fraction of HCl

  13. Solution Formation Formation of a solution involves 3 steps • Separate the solute particles • expand the solute • Separate the solvent particles • Expand the solvent • Form the solution • Solute and solvent interact

  14. Solution Formation • Each step of solution formation involves energy and has a DH. DH1 = energy needed to separate the solute DH2 = energy needed to separate the solvent DH3 = energy released when solution forms

  15. Solution Formation DHsolution = DH1 +DH2 +DH3 Solutions form when the DHsolution is a small value – see page 504

  16. Factors Impacting Solubility • Structure – like dissolves like • #44 on page 533

  17. Factors Impacting Solubility • Pressure • Pressure has little impact on the solubility of liquids and solids • Pressure has a significant impact on the solubility of gases in a liquid • The higher the pressure of gaseous solute above a liquid the higher the concentration of the gas in the solution

  18. Henry’s Law • Henry’s Law: C = kP C = Concentration of dissolved gas k = solution specific constant P = partial P of the solute gas above the solution • What does Henry’s Law mean? • No calculations required. Page 506

  19. Temperature and Solubility • Temperature has variable effects on the amount of solid that will dissolve in an aqueous solution! • See figure 11.6 page 508 • Solutes will dissolve more rapidly at higher temperatures

  20. Temperature and Solubility • The solubility of a gas in water decreases as temperature increases. • See figure 11.7 on page 508 • Thermal pollution – read the story on page 510 when you get a chance

  21. Vapor Pressure of Solutions • See Raoult’s Law on page 510 • Psolution= csolvent P0solvent

  22. Colligative Properties • Colligative properties • properties of a solution that depend upon the amount of dissolved solute, not the identity of the solute. • Freezing point depression • Boiling point elevation • Osmotic Pressure • Note: I will be weaving section 11.7 and the van’t Hoff factor (i) into my consideration of these properties and not consider it separately.

  23. Colligative Properties • FP = Kf m i • BP = Kb m i See page 517 for needed constants

  24. Calculating the bp or fp of a solution • Calculating the molar mass of a solute from fp or bp data

  25. Osmotic Pressure • Osmotic Pressure (P) is often used to determine the molar mass of large biological molecules P = MRTi

More Related