Chap. 12 -- Colligative Properties

vapor pressure

pressure exerted by gas in equilibrium w/ liquid phase at given temp

volatile

having significant vapor pressure at given temp

• higher vapor pressure = more volatile

presence of nonvolatile solute

affects rate of evaporation, decreases vapor pressure of solution compared to pure solvent

Raoult’s Law

P_solution = x_solventP_solevent

• _{vapor pressure of volatile solvent lowered by presence of nonvolatile solute}

• _{more nonvolatile solute particles = lower vapor pressure of solution}

Boiling Point Elevation

decrease in vapor pressure of solution of pure substance at all temperatures corresponds to increase in boiling point

Freezing point depression

solutions freeze at lower temperatures than pure solvents

molality

m=\frac{n_{solute}}{\operatorname{kg}solvent}   

• used when calculating boiling point elevation/freezing point depression

hypertonic (osmosis)

higher concentration of solutes inside

net osmotic flow out = cell shrinks

isotonic (osmosis)

match in concentration

no net osmotic flow = no change in cell

hypotonic (osmosis)

lower concentration inside cell

net osmotic flow into cell = cell expands

colligative property

characteristics of solutions depending on concentration

osmotic pressure

II = iMRT

• M = total molar concentration 

• R = gas law constant

• T = absolue temp

van’t Hoff Factor

ratio of concentrations of solute particles : concentration of potential particles if solute didn’t dissociate

ion pair (van’t Hoff)

cluster formed when cation & anion associate w/ each other

desalination (reverse osmosis)

process involving removing most ions from seawater

Henry’s Law

C_{gas}=k_{H}P_{gas}

• C_gas → maximum concentration of gas

• k_H → constant for gas

• P_{gas → partial pressure of gas}