2 Classification of Matter Solutions are homogeneous mixtures
3 Solute Solvent A solute is the dissolved substance in a solution. Salt in salt waterSugar in soda drinksCarbon dioxide in soda drinksSolventA solvent is the dissolving medium in a solution.Water in salt waterWater in soda
4 Calculations of Solution Concentration Mass percent - the ratio of mass units of solute to mass units of solution, expressed as a percent
5 Calculations of Solution Concentration Mole fraction – the ratio of moles of solute to total moles of solution
6 Calculations of Solution Concentration Molality – moles of solute per kilogram of solvent
7 Calculations of Solution Concentration Molarity - the ratio of moles of solute to liters of solution
8 Heat of SolutionThe Heat of Solution is the amount of heat energy absorbed (endothermic) or released (exothermic) when a specific amount of solute dissolves in a solvent.SubstanceHeat of Solution(kJ/mol)NaOH-44.51NH4NO3+25.69KNO3+34.89HCl-74.84
9 Steps in Solution Formation H1 Expanding the soluteSeparating the solute into individual componentsH2 Expanding the solventOvercoming intermolecular forces of the solvent moleculesH3 Interaction of solute and solvent toform the solution
10 “Like Dissolves Like”Nonpolar solutes dissolve best in nonpolar solventsFatsBenzeneSteroidsHexaneWaxesToluenePolar and ionic solutes dissolve best in polar solventsInorganic SaltsWaterSugarsSmall alcoholsAcetic acid
12 Solubility TrendsThe solubility of MOST solids increases with temperature.The rate at which solids dissolve increases with increasing surface area of the solid.The solubility of gases decreases with increases in temperature.The solubility of gases increases with the pressure above the solution.
13 Therefore… Solids tend to dissolve best when: Heated Stirred Ground into small particlesLiquids tend to dissolve best when:The solution is coldPressure is high
14 Saturation of Solutions A solution that contains the maximum amount of solute that may be dissolved under existing conditions is saturated.A solution that contains less solute than a saturated solution under existing conditions is unsaturated.A solution that contains more dissolved solute than a saturated solution under the same conditions is supersaturated.
16 Henry’s LawThe concentration of a dissolved gas in a solution is directly proportional to the pressure of the gas above the solutionApplies most accurately for dilute solutions of gases that do not dissociate or react with the solventYes CO2, N2, O2No HCl, HI
17 Raoult’s Law Psolution = Observed Vapor pressure of The presence of a nonvolatile solute lowers the vapor pressure of the solvent.Psolution = Observed Vapor pressure ofthe solutionsolvent = Mole fraction of the solventP0solvent = Vapor pressure of the pure solvent
18 Liquid-liquid solutions in which both components are volatile Modified Raoult's Law:P0 is the vapor pressure of the pure solventPA and PB are the partial pressures
19 Raoult’s Law – Ideal Solution A solution that obeys Raoult’s Law is called an ideal solution
20 Negative Deviations from Raoult’s Law Strong solute-solvent interaction results in a vapor pressure lower than predictedExothermic mixing = Negative deviation
21 Positive Deviations from Raoult’s Law Weak solute-solvent interaction results in a vapor pressure higher than predictedEndothermic mixing = Positive deviation
22 Definition of Electrolytes and Nonelectrolytes An electrolyte is:A substance whose aqueous solution conductsan electric current.A nonelectrolyte is:A substance whose aqueous solution does notconduct an electric current.Try to classify the following substances aselectrolytes or nonelectrolytes…
23 Electrolytes vs. Nonelectrolytes The ammeter measures the flow of electrons (current)through the circuit.If the ammeter measures a current, and the bulbglows, then the solution conducts.If the ammeter fails to measure a current, and thebulb does not glow, the solution is non-conducting.
24 Electrolytes? Pure water Tap water Sugar solution Sodium chloride solutionHydrochloric acid solutionLactic acid solutionEthyl alcohol solutionPure sodium chloride
25 Answers to Electrolytes NONELECTROLYTES:Tap water (weak)NaCl solutionHCl solutionLactate solution (weak)Pure waterSugar solutionEthanol solutionPure NaCl
26 Colligative Properties Colligative properties are those that depend on the concentration of particles in a solution, not upon the identity of those properties.Boiling Point ElevationFreezing Point DepressionOsmotic Pressure
27 Freezing Point Depression Each mole of solute particles lowers the freezing point of 1 kilogram of water by 1.86 degrees Celsius.Kf = 1.86 C kilogram/molm = molality of the solutioni = van’t Hoff factor
28 Boiling Point Elevation Each mole of solute particles raises the boiling point of 1 kilogram of water by 0.51 degrees Celsius.Kb = 0.51 C kilogram/molm = molality of the solutioni = van’t Hoff factor
29 Freezing Point Depression and Boiling Point Elevation Constants, C/m SolventKfKbAcetic acid3.903.07Benzene5.122.53Nitrobenzene8.15.24Phenol7.273.56Water1.860.512
30 The van’t Hoff Factor, iElectrolytes may have two, three or more times the effect on boiling point, freezing point, and osmotic pressure, depending on its dissociation.
31 Dissociation Equations and the Determination of i NaCl(s) Na+(aq) + Cl-(aq)i = 2AgNO3(s) Ag+(aq) + NO3-(aq)i = 3MgCl2(s) Mg2+(aq) + 2 Cl-(aq)i = 3Na2SO4(s) 2 Na+(aq) + SO42-(aq)AlCl3(s) Al3+(aq) + 3 Cl-(aq)i = 4
32 Ideal vs. Real van’t Hoff Factor The ideal van’t Hoff Factor is only achieved in VERY DILUTE solution.
33 Osmotic PressureThe minimum pressure that stops the osmosis is equal to the osmotic pressure of the solution
34 Osmotic Pressure Calculations M = Molarity of the solutionR = Gas Constant = Latm/molK = Osmotic pressure
35 Suspensions and Colloids Suspensions and colloids are NOT solutions.Suspensions: The particles are so large that they settle out of the solvent if not constantly stirred.Colloids: The particles intermediate in size between those of a suspension and those of a solution.
36 Types of Colloids Examples Dispersing Medium Dispersed Substance Colloid TypeFog, aerosol spraysGasLiquidAerosolSmoke, airborn germsSolidWhipped cream, soap sudsFoamMilk, mayonnaiseEmulsionPaint, clays, gelatinSolMarshmallow, StyrofoamSolid FoamButter, cheeseSolid EmulsionRuby glassSolid sol
37 The Tyndall EffectColloids scatter light, making a beam visible. Solutions do not scatter light.Which glass contains a colloid?colloidsolution