Question

If a small amount of the benzoic acid measured fails to dissolve in the lauric acid, what impact would this have on the molecular weight calculated? Would it be too high or too low? Explain your answer

Answer 1

(answer) here the impact is calculated molecular weight will be higher. here a small amount benzoic acid is fails to dissolve in lauric acid ,the depression in freezing point will be lower. depression of freezing point is a colligative property. the  properties of dilute solution which depends on the number of solute particles present in a given amount of solvent and not in any way upon the nature of solute particles are called colligative properties.

depression of freezing point , Tf = ( mass / molar mass of solute) Kf (1)

Kf = molal depression constant,

Kf = KM1 / 1000 ;

M1 = molar mass of solvent , K = constant

here the molecular weight of benzoic acid (solute)calculated increases , because the freezing point depression inversely proportional to the molar mass of solute.

Tf 1 / (molar mass of solute) from equation (1)