CHAPTER 22 COLLIGATIVE AND COLLOIDAL PROPERTIES

22-1 Raoult's law

colligative properties: vapor pressure/freezing point depression/

boiling point elevation/rate of diffusion through a membrane

colligative properties depend on the number of particles in

solution

raoult's law: the vapor pressure of a solution varies directly

as the mole fraction of solvent

in an ideal solution all intermolecular attractions are the same

the ratio of molecules in a liquid solution will not always be

the same ratio for the vapor

liquid ratio= 1:1 vapor ratio= 3.34:1

vapor pressure of a solution is the sum of the normal vapor

pressure of each component multiplied by its mole fraction

in the solution

22-2 fractional distillation

fractional distillation depends upon vapor pressure differences

22-3 boiling point and freezing point

the bp of a liquid is the T at which the vapor pressure of the

liquid equals the atmospheric pressure(liquid->gas)

condensation point is same but is for gas->liquid

the fp of a liquid is the T at which the vapor pressure of the

solid and liquid are equal(solid->liquid). mp is same but

is for liquid->solid

the addition of a nonvolatile solute to a liquid causes both

a bp elevation and a fp depression

22-4 calculating fp and bp

when determining significant digits consider 100C and 0C points

to be exact because the celsius scale is defined by these

POINTS

molal bp elevation for water is .515 C

molal fp depression for water is 1.853 C

22-5 experimental determination of molecular mass

molecular mass of a solute may be determined by dissolving a

known mass of solvent and measuring the resulting shift

in freezing or boiling point

22-6 osmotic pressure

semipermeable membranes will allow small particles(ions and

molecules) to pass through, but will stop large molecules

osmotic pressure is the pressure needed to prevent the net flow

of solvent from the pure solvent into a solution of the

solvent/ unequal passing of particles causes a pressure to

be built up between the two sides of the membrane/it is a

colligative property

II=MRT II=osmotic pressure/M=molarity/R=ideal gas constant

T=kelvin temp

22-7 Nonideal solutions

nonideal activity is due to ion interaction

ideal solutions obey raoults law. some ionic solutions deviate

because of attractive forces between ions of opposite

charges

22-8 colloids and phases

crystalloids pass readily through a parchment membrane

colloids will not pass through a membrane/mixture composed of

2 phases of matter-the dispersed phase and continuous

phase. they are an intermediate class between suspensions

and solutions

22-9 colloidal size

suspensions contain large particles in solution that will

settle out upon standing

colloid chemistry is defined as the study of the properties of

matter whose particles are colloidal in size in at least

one dimension

solution <1nm size

colloid >1nm but <100nm

suspension>100nm(will settle out)

22-10 properties of colloids

tyndall effect: the scattering of light by colloidal particles

brownian motion: is the constant random movement of colloidal

particles

electrophoresis is the migration of charged colloidal particles

within an electric field