Chapter 11Properties of Solutions

11-1 Solution Composition (pg. 512)11-2 The Energies of Solution Formation (pg. 515)

11-3 Factors Affecting Solubility (pg.. 519)11-4 The Vapor Pressures of Solutions (pg.. 524)

11-5 Boiling Point Elevation and Freezing Point Depression (pg. 531)11-6 Osmotic Pressure (pg. 535)

11-7 Colligative Properties of Electrolyte Solutions (pg. 540)11-8 Colloids (pg. 543)Equations to Memorize

11-1 Solution Composition (pg.512)

Concentration Units Molarity (M) - number of moles of solute per liter solution

M = Moles of Soluteliters of solution

Molality(m) – number of moles of solute per kilogram of solvent

m= Moles of Solutekilogram of solvent

For Dilute aqueous solutions, Molarity = Molality

Mole Fraction and Mole Percent

Mole Percent= molesof componenttotalmoles of solution

×100 %

11-2 The Energies of Solution Formation (pg.515)

★Enthalpy of solution (ΔHsoln) - Total amount of energy released during a chemical reaction

ΔHsoln = ΔH1 + ΔH2 + ΔH3

Enthalpy (heat) of hydration (ΔHhyd) – enthalpy change associated with the dispersal of a gaseous solute in water.

Processes that require large amounts of energy tend not to occur

11-3 Factors Affecting Solubility (pg. 519)

There are three main factors that affect the solubility: Structure Effects Pressure Effects Temperature Effects

Structure Effects

Solubility of a solute in a solvent purely depends on the nature of both solute and solvent

- Solubility of a non-polar solute in a solvent is large- Polar solute has low solubility or insoluble in a non-polar solvent

Pressure Effects

Solids and Liquids: changes in pressure have practically no effect on solubility.

Gases: increases the solubility with increased pressure

Henry's LawSg = kH Pgas

Temperature

Solids: Solubility increases with temperature

Gases: Less soluble as temperature increases

11-4 The Vapor Pressures of Solutions (pg. 524)

Vapor Pressures - equilibrium pressure of gas molecules from that liquid above the Liquid itself

The vapor pressure of a solvent depends on how pure it is And…

Nonvolatile solute lowers the vapor pressure of a solvent.

where

Po = vapor pressure of the pure solvent

Non-ideal solutions

-Solutions with positive deviations from Raoult’s law have vapor pressures which are higher than Raoult’s law.

-Solutions with negative deviations from Raoult’s law

11-5 Boiling Point Elevation and Freezing Point Depression (pg. 531)

ΔNormal boiling point of a liquid occurs at the temperature where the vapor pressure is equal to 1 atm.

Boiling-point elevation: 1) Non-volatile solute elevates the boiling point of the solvent.2) The magnitude of the boiling-point elevation depends on the

concentration of the solute’

ΔTbp = Kbp msoluteKbp = molal boiling

point elevation constant (oC/m)

Freezing-point elevation:

Vapor Pressure lowering lowers the freezing-point of the solution

ΔTfp = Kfp msoluteKfp = molal freezing

point elevation constant (oC/m)

∴The addition of solute RAISES the boiling point

The addition of solute LOWERS the freezing point

11-6 Osmotic Pressure (pg. 535)

Osmosis: The movement of solvent molecules through a semipermeable membrane from a region of lower solute concentration to a region of higher solute concentration.

The minimum pressure that stops the osmosis is equal to the osmotic pressure of the solution

OSMOTIC PRESSURE FORMULA

Osmotic pressure has a great effect on living cells (their walls are semipermeable)

Reverse Osmosis

Providing a pressure greater than the osmotic pressure to reverse the flow of solvent particles

Dialysis

The preventing of semipermeable membrane from transferring all solute particles.

11-7 Colligative Properties of Electrolyte Solutions (pg. 540)

Colligative PropertiesPhysical properties of solutions that depend on the number of solute

particles present but not on the identity of the solute

The relationship between the moles of solute dissolved and the moles of particles in solution is expressed using the van’t Hoff factor.

i=molesof particles∈solutionmolesof solute dissolved

Ion pairing = a pair of oppositely charged ions held together by Coulomb attraction without formation of a covalent bond.

ΔT = imK π = iMRT

11-8 Colloids (pg. 543)

Solutions: Relatively small particles; homogeneous mixture; no settling

Suspensions: Larger particles that can “settle out” (sand in water)

Colloids: Higher molar masses; relatively large diameters; they do not settle out

Tyndall Effect: scattering of light by particles

Coagulation : destruction of a colloid. Equations to Memorize