*Degree of saturationSaturated solutionSolvent holds as much solute as is possible at that temperature.Undissolved solid remains in flask.Dissolved solute is in dynamic equilibrium with solid solute particles.

*Degree of saturationUnsaturated SolutionLess than the maximum amount of solute for that temperature is dissolved in the solvent.No solid remains in flask.

*Degree of saturationSupersaturatedSolvent holds more solute than is normally possible at that temperature.These solutions are unstable; crystallization can often be stimulated by adding a seed crystal or scratching the side of the flask.

*Degree of saturationUnsaturated, Saturated or Supersaturated?

How much solute can be dissolved in a solution?

More on this in Chap 17(solubility products, p 739)

*Factors Affecting SolubilityChemists use the axiom like dissolves like:Polar substances tend to dissolve in polar solvents.Nonpolar substances tend to dissolve in nonpolar solvents.

*Factors Affecting SolubilityThe stronger the intermolecular attractions between solute and solvent, the more likely the solute will dissolve.Example: ethanol in waterEthanol = CH3CH2OHIntermolecular forces = H-bonds; dipole-dipole; dispersion

Ions in water also have ion-dipole forces.

*Factors Affecting SolubilityGlucose (which has hydrogen bonding) is very soluble in water.Cyclohexane (which only has dispersion forces) is not water-soluble.

*Factors Affecting SolubilityVitamin A is soluble in nonpolar compounds (like fats).Vitamin C is soluble in water.

*Which vitamin is water-soluble and which is fat-soluble?

*Gases in SolutionIn general, the solubility of gases in water increases with increasing mass.Why?Larger molecules have stronger dispersion forces.

*Gases in Solution

*Gases in SolutionThe solubility of liquids and solids does not change appreciably with pressure.But, the solubility of a gas in a liquid is directly proportional to its pressure.Increasing pressure above solution forces more gas to dissolve.

*Henrys LawSg = kPg whereSg is the solubility of the gas;k is the Henrys law constant for that gas in that solvent;Pg is the partial pressure of the gas above the liquid.

*Henrys LawSg = kPgk for N2 at 25=6.8 x 10-4 mol/L atm

*TemperatureGenerally, the solubility of solid solutes in liquid solvents increases with increasing temperature.

*TemperatureThe opposite is true of gases. Higher temperature drives gases out of solution.

Carbonated soft drinks are more bubbly if stored in the refrigerator.Warm lakes have less O2 dissolved in them than cool lakes.

*Chap 13: Ways of Expressing Concentrations of Solutions

*Mass PercentageMass % of A = 100

*Parts per Million andParts per Billionppm = 106Parts per Million (ppm)Parts per Billion (ppb)ppb = 109

*Mole Fraction (X)In some applications, one needs the mole fraction of solvent, not solutemake sure you find the quantity you need!

*Molarity (M)You will recall this concentration measure from Chapter 4.Because volume is temperature dependent, molarity can change with temperature.

*Molality (m)Because neither moles nor mass change with temperature, molality (unlike molarity) is not temperature dependent.

*Mass/MassMoles/MolesMoles/MassMoles/L

*Changing Molarity to MolalityIf we know the density of the solution, we can calculate the molality from the molarity, and vice versa.

*PRACTICE EXERCISE(a) Calculate the mass percentage of NaCl in a solution containing 1.50 g of NaCl in 50.0 g of water. (b) A commercial bleaching solution contains 3.62 mass % sodium hypochlorite, NaOCl. What is the mass of NaOCl in a bottle containing 2500 g of bleaching solution?PRACTICE EXERCISEA commercial bleach solution contains 3.62 mass % NaOCl in water. Calculate (a) the molality and (b) the mole fraction of NaOCl in the solution.

*PRACTICE EXERCISE(a) Calculate the mass percentage of NaCl in a solution containing 1.50 g of NaCl in 50.0 g of water. (b) A commercial bleaching solution contains 3.62 mass % sodium hypochlorite, NaOCl. What is the mass of NaOCl in a bottle containing 2500 g of bleaching solution?Answers:(a) 2.91%, (b) 90.5 g of NaOClAnswers: (a) 0.505 m, (b) 9.00 103

*Colligative PropertiesColligative properties depend only on the number of solute particles present, not on the identity of the solute particles.Among colligative properties areVapor pressure lowering Boiling point elevationMelting point depressionOsmotic pressure

*********Figure: 13-32-03UNE13.06

Title: Exercise 13.6

Caption: Vitamins E and B6.*****************