Chapter 12, pp 401-424

Solutions

Types of Mixtures• Homogeneous mixtures

- SolutionsSolvent = 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, MgBr2, 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 H2O vs. Temperature

20

40

60

00 20 40 60 80 100

Saturated

Supersaturated

Unsaturated

Temperature, o C

Gra

ms

per

100g

H2O

Solubility Curve