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Properties of Solutions

Properties of Solutions. Brown, LeMay Ch 13 AP Chemistry. CaCl 2 (aq). 13.1: Types of Solutions. When do solutions form?. Solutions form (the solute and solvent will mix) when: Energy: solute-solvent interactions are stronger than solute-solute or solvent-solvent interactions.

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Properties of Solutions

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  1. Properties of Solutions Brown, LeMay Ch 13 AP Chemistry CaCl2 (aq)

  2. 13.1: Types of Solutions

  3. When do solutions form? • Solutions form (the solute and solvent will mix) when: • Energy:solute-solvent interactions are stronger than solute-solute or solvent-solvent interactions. • Disorder:Solutions result in a more disordered state than the separate solute and solvent states, since molecules will be “mixed” that were once “well organized”. NaCl (s) + H2O (l) → Na+ (aq) + Cl- (aq) • Ion-dipole interactions > H-bonds (H2O···H2O) < Ionic bonds (Na+ Cl-) • The increase in disorder also drives the dissolving process. http://phet.colorado.edu/en/simulation/soluble-salts

  4. 13.2: Ways to Express Concentration • Molarity:commonly used for solutions • Varies with T Partner Activity: How do you make I M 500 mL NaCl solution?

  5. 13.3: Solubility Vocabulary • Solvation:dissolving; the interactions between solute and solvent • Hydration: solvation with water • Crystallization: “un-dissolving”; process by which solute particles leave the solvent. • Solute + solvent ↔ solution (equilibrium)

  6. 13.3: Solubility Vocabulary • http://www.youtube.com/watch?v=VTmfQUNLlMY • Saturated: a solution that is in equilibrium with undissolved solute (appears as solution and crystals) • Solubility: the amount of solute needed to form a saturated solution • Unsaturated:a solution containing less than the saturated amount (appears as solution only) • Supersaturated: a solution containing more than the saturated amount, yet appears unsaturated.

  7. Solubility Solubility: go to the temperature and up to the desired line, then across to the Y-axis. This is how many g of solute are needed to make a saturated solution of that solute in 100g of H2O at that particular temperature. At 40oC, the solubility of KNO3 in 100g of water is 64 g. In 200g of water, double that amount. In 50g of water, cut it in half.

  8. Supersaturated If 120 g of NaNO3 are added to 100g of water at 30oC: 1) The solution would be SUPERSATURATED, because there is more solute dissolved than the solubility allows 2) The extra 25g would precipitate out 3) If you heated the solution up by 24oC (to 54oC), the excess solute would dissolve.

  9. Unsaturated If 80 g of KNO3 are added to 100g of water at 60oC: 1) The solution would be UNSATURATED, because there is less solute dissolved than the solubility allows 2) 26g more can be added to make a saturated solution 3) If you cooled the solution down by 12oC (to 48oC), the solution would become saturated

  10. 13.4: Factors Affecting Solubility • “Like dissolves like.” • Miscible: liquids that mix (polar or ionic solute with polar solvent, or nonpolar with nonpolar) • Immiscible:liquids that do not mix (polar or ionic solute with nonpolar solvent) • Covalent network solids do not dissolve in polar or nonpolar solvents.

  11. 13.4: Factors Affecting Solubility • Pressure: does not significantly affect solubility of liquids and solids • Gases: increased P means increased solubility Henry’s law: Cg = k Pg Cg = solubility of gas in solution (M) k = Henry’s law constant Pg = partial pressure of gas over solution http://wps.prenhall.com/wps/media/objects/1055/1080459/media/AABTGZG0.html William Henry(1775-1836)

  12. 13.4: Factors Affecting Solubility • Temperature • Most solids: increased T means increased solubility • * Exception: Ce2(SO4)3 • Gases: increased T means decreased solubility

  13. Reference Table H: Vapor Pressure of Four Liquids (c) 2006, Mark Rosengarten

  14. 13.6: Colloids • Mixtures containing particles intermediate between: • A solution (homogeneous, < 10 Å) and • A suspension (heterogeneous, > 2000 Å) • Tyndall effect:scattering of lightseen in a colloid John Tyndall(1820-1893)

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