Chapter 12, pp Solutions

Types of Mixtures Homogeneous mixtures - Solutions Solvent = dissolving medium (like water) Solute = substance dissolved (like sugar) May exist as liquid, gas, or solid (alloys) Heterogeneous mixtures

Mixtures Homogeneous - Solutions Heterogeneous –Suspensions: particles settle out –Colloids: dispersion Emulsions – milk, mayonnaise, cheese, butter Foam – shaving cream, whipped cream Gels - gelatin Aerosol – smoke, fog, clouds, mist, exhaust Sol – paints, mud

Solutes Electrolytes –Conducts electricity in aqueous sol’n –Salts (NaCl, HCl, MgBr 2, etc…) Nonelectrolytes –Does NOT conduct electricity –Sugars, nonpolar molecules

Solution Process Factors affecting rate of dissolution –Surface area of solute –Kinetic energy (agitation) –Temperature (usually heat is better) –Concentration (amount of solute per solvent) –Polar vs. nonpolar (“Like dissolves like.”) –Pressure (gas in liquids) Henry’s Law

Enthalpies of Solution Changes in molecular bonds are required  Solute-solute; solvent-solvent Solvation involves changes in energy –Heat absorbed by solution (endothermic) KI dissolved in water feels cold –Heat released by solution (exothermic) NaOH dissolved in water feels warm

Concentrations of Sol’n Molarity –Moles of solute/ Liter of sol’n  “M” Molality –Moles of solute/ Kilogram of solvent  “m” Normality (FYI) –One gram equivalent of solute/ Liter of sol’n  “N”

Saturation Saturated = contains max am’t of solute Unsaturated = less than max amount Supersaturated = more than saturated –Heat solvent as solute is added –Leave undisturbed –Crystal formation returns sol’n to equilibrium

Saturation Curve Mass (grams) per 100g H 2 O vs. Temperature  Saturated Supersaturated Unsaturated Temperature, o C Grams per 100g H 2 O

Solubility Curve