2 Various Types of Solutions ExampleState of SolutionState of SoluteState of SolventAir, natural gasGasVodka, antifreezeLiquidBrassSolidCarbonated water (soda)Seawater, sugar solutionHydrogen in platinumSolvent is majority component. Solute is minority component, usually the substance dissolved in the solvent (liquid).
4 MolarityYou have 1.00 mol of sugar in mL of solution. Calculate the concentration in units of molarity.8.00 MYou have a 10.0 M sugar solution. What volume of this solution do you need to have 2.00 mol of sugar?0.200 L
5 Molarity (M) exampleConsider separate solutions of NaOH and KCl made by dissolving g of each solute in mL of solution. Calculate the concentration of each solution in units of molarity.10.0 M NaOH5.37 M KCl
6 Mass percent (%)What is the percent-by-mass concentration of glucose in a solution made my dissolving 5.5 g of glucose in 78.2 g of water?6.6%
7 Mole fraction (A)A solution of phosphoric acid was made by dissolving 8.00 g of H3PO4 in mL of water. Calculate the mole fraction of H3PO4. (Assume water has a density of 1.00 g/mL.)0.0145
8 Molality (m)A solution of phosphoric acid was made by dissolving 8.00 g of H3PO4 in mL of water. Calculate the molality of the solution. (Assume water has a density of 1.00 g/mL.)0.816 m
10 Solution Formation Process Separating the solute into its individual components (expanding the solute).Overcoming intermolecular forces in the solvent to make room for the solute (expanding the solvent).Allowing the solute and solvent to interact to form the solution.
11 Solution Formation Energies Steps 1 and 2 require energy, since forces must be overcome to expand the solute and solvent.Step 3 usually releases energy.Steps 1 and 2 are endothermic, and step 3 is often exothermic.Enthalpy change associated with the formation of the solution is the sum of the ΔH values for the steps:ΔHsoln = ΔH1 + ΔH2 + ΔH3ΔHsoln may have a positive sign (energy absorbed) or a negative sign (energy released).
12 Exo vs. Endo HsolnDemo NH4NO3 and NaOH examples
13 Explain why water and oil (a long chain hydrocarbon) do not mix Explain why water and oil (a long chain hydrocarbon) do not mix. In your explanation, be sure to address how ΔH plays a role.H1H2H3HsolnOutcomePolar solute, polar solventLargeLarge, negativeSmallSolution formsNonpolar solute, polar solventLarge, positiveNo solution formsNonpolar solute, nonpolar solventPolar solute, nonpolar solvent
15 Pressure effects Henry’s law: C = kP C = concentration of dissolved gask = constantP = partial pressure of gas solute above the solutionAmount of gas dissolved in a solution is directly proportional to the pressure of the gas above the solution.
16 Gas solubility in liquid Soda pop’s carbonated water has the carbon dioxide forced into the solution under pressure. When the can is opened Patm is much lower than Pcan so CO2 leaves -> pop goes flat.
17 Temperature effectsAlthough the solubility of most solids in water increases with temperature, the solubilities of some substances decrease with increasing temperature.Predicting temperature dependence of solubility is very difficult.Solubility of a gas in solvent typically decreases with increasing temperature.
19 Colligative Properties Depend only on the number, not on the identity, of the solute particles in an ideal solution:Vapor pressure loweringBoiling-point elevationFreezing-point depressionOsmotic pressure
20 Vapor Pressure of solutions If the Pvap of the solvent (water) > Pvap of the solution, equilibrium is reached when the solvent evaporates and the solvent is absorbed by solution. It does this to lower the Pvap towards its equilibrium value.
21 Raoult’s LawNonvolatile solute lowers the vapor pressure of a solvent.Raoult’s Law:Psoln = observed vapor pressure of solutionsolv = mole fraction of solventPosolv = vapor pressure of pure solvent
22 Raoult’s Law - ideal solution Ideal solution occurs with a nonvolatile solute in solutionAlso the vapor pressure is then proportional to the mole fraction of the solvent using (total moles of ions of solute) in the solvent
23 Boiling Point elevation Nonvolatile solute elevates the boiling point of the solvent.ΔT = KbmsoluteΔT = boiling-point elevationKb = molal boiling-point elevation constantmsolute= molality of solute particles
24 Freezing Point depression When a solute is dissolved in a solvent, the freezing point of the solution is lower than that of the pure solvent.ΔT = KfmsoluteΔT = freezing-point depressionKf = molal freezing-point depression constantmsolute= molality of solute particles
27 Boiling Pt Elev Problem A solution was prepared by dissolving g glucose in g water. The molar mass of glucose is g/mol. What is the boiling point of the resulting solution (in °C)? Glucose is a molecular solid that is present as individual molecules in solution. Kb = 0.51oC.kg/mol°C
28 Osmotic PressureOsmosis – flow of solvent into the solution through a semipermeable membrane. (Kidney dialysis uses this Principle).= MRT= osmotic pressure (atm)M = molarity of the solutionR = gas law constantT = temperature (Kelvin)
30 Osmotic Pressure Problem When 33.4 mg of a compound is dissolved in 10.0 mL of water at 25°C, the solution has an osmotic pressure of 558 torr. Calculate the molar mass of this compound.Strategy: need Temp in K, Pressure in atm, use R with atm unit to get molarity. Then use vol get moles, then mass get molar mass.111 g/mol
31 ColloidsIntermediate mixture - a heterogeneous mixture with particle size between a suspension and a solutionA suspension of tiny particles in some medium.Tyndall effect – scattering of light by particles.Suspended particles are single large molecules or aggregates of molecules or ions ranging in size from 1 to 1000 nm.
34 Freezing Pt problemYou take 20.0 g of a sucrose (C12H22O11) and NaCl mixture and dissolve it in 1.0 L of water. The freezing point of this solution is found to be °C. Kf = 1.86oC.kg/molAssuming ideal behavior, calculate the mass percent composition of the original mixture, and the mole fraction of sucrose in the original mixture.72.8% sucrose and 27.2% sodium chloride;mole fraction of the sucrose is 0.313
35 Derivation of Colligative Properties Specific derivation of the partial derivatives and derivation for colligative properties are found on the website.