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

13.1: Types of Solutions Example Solvent Solute Air (g in g) Soda (g in l) H2 in Pt (g in s) Alcoholic beverages (l in l) Sea water (s in l) Brass (s in s) N2 O2 H2O CO2 Pt H2 H2O C2H5OH H2O NaCl (one of many salts) Copper (55% – 90%) Zinc (10% – 45%)

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

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?

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)

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.

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.

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.

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

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.

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 English chemist; He began to study medicine at Edinburgh in 1795, taking his doctor's degree in 1807, but ill-health interrupted his practice as a physician, and he devoted his time mainly to chemical research, especially with regard to gases, 1803. His Elements of Experimental Chemistry (1799) enjoyed considerable vogue in its day, going through xi editions in 30 years. This book was also translated in Japanese in 1840, as part of the Western studies "Rangaku" movement William Henry (1775-1836)

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

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

13.6: Colloids A solution (homogeneous, < 10 Å) and Mixtures containing particles intermediate between: A solution (homogeneous, < 10 Å) and A suspension (heterogeneous, > 2000 Å) Tyndall effect: scattering of light seen in a colloid British, contemporary of Faraday and Darwin, early proponent of evolutionary theory; amazing public speaker; did a free science tour in USA in 1872. John Tyndall (1820-1893)