Chapter 12, pp 401-424 Solutions. Types of Mixtures Homogeneous mixtures - Solutions Solvent =...
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Transcript of Chapter 12, pp 401-424 Solutions. Types of Mixtures Homogeneous mixtures - Solutions Solvent =...
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