solutions- colligative properties (isotonicity)

molarity

the number of moles of solute in 1L of solution

molality

the number of of moles of solute in 1000g of solvent

mole fraction

the number of moles of solute divided by the total number of moles of solute and solvent

%w/v

g of solute in 100 ml in solution

%w/w

g of solute in 100g of solution

raoults law

• the partial pressure of a substance in a liquid mixture is proportional to its mole fraction

• best suited to describe the vapour pressure of the solvent in a very dilute solution

is vapour pressure of the solute proportional to its mole fraction in dilute solution

yes

henrys law

• obeyed at very low concentrations of the solute e.g. ideal-dilute solution

what are the 3 main effects of a non-volatile solute

• raises the boiling point of a solution

• lowers the freezing point

• gives rise to osmotic pressure

what are Kb and Kf called

ebulioscopic and cyroscopic constants of the solvent

important assumptions about colligative properties

• solute is not volatile and does not appear in the vapour phase

• solute is insoluble in the solid solvent and therefore does not appear in the solid phase

depression of the freezing point

Tf= KfbB

elevation of boiling point

Tb= KbbB

what is boiling point elevation

a consequence of the vapour pressure lowering by the presence of solute particles

when is a solution said to be isotonic

if it has the same osmotic pressure as a reference body fluid, measured with respect to the appropriate body membrane