Question

Students prepared two cyclohexane solutions having the same mass of solute. However, Student 1 used 13.354 g of cyclohexane, Student 2 used 15.339 g. Which Student will observe the larger change in the freezing point? Explain.

Answer 1

If same solvent, then

dTf = -Kf*m*i

Kf =depression constant, unique for solvent, won't be affected

i = vant hoff factor for electrolye, will not change with addition of solvent

molality = mol of solute / kg solvent

if we increase solvent, then we decrease molality, which makes a smaller effect in freezing temperature

therefore

the one that uses 15.339 g of solvent, will have less molality, therefore the change of Freezing point (i.e. depression pooint) will not be that strong.

the larger change is given when

solvent = 13.354 g are used