Camphor, C10H16O, with a fragrant and penetrating odor is used in used in cosmetics as a preservative. camphor has a normal freezing point of 178.8 degrees celsius and Kf of 37.3 C/m. When a 2.96 grams sample of a nonelectrolyte with an emperical formula of C2H4Cl is dissolved in 47.21 g of camphor, the freezing point of the solution is 160.4 degrees celsius. What are the molecular weight, and molecular formula of the solute?
Ans: 127g/mol

We have not covered these kinds of problems yet in my class, but I will go on vacation tomorrow. Can anyone teach me how to do this? Thanks! :)

Question

Camphor, C10H16O, with a fragrant and penetrating odor is used in used in cosmetics as a preservative. camphor has a normal freezing point of 178.8 degrees celsius and Kf of 37.3 C/m. When a 2.96 grams sample of a nonelectrolyte with an emperical formula of C2H4Cl is dissolved in 47.21 g of camphor, the freezing point of the solution is 160.4 degrees celsius. What are the molecular weight, and molecular formula of the solute?
Ans: 127g/mol

We have not covered these kinds of problems yet in my class, but I will go on vacation tomorrow. Can anyone teach me how to do this? Thanks! :)

aaronq · Answer

to solve a question like this, all you need is the freezing-point depression formula:

ΔT=i∗m∗Kf


dT= change in temperature (of the freezing point)
i= van't hoff factor (for this question the substance doesn't dissociate so i=1)
m=molality = moles of solute/Kg of solvent
Kf=freezing-point depression constant

You should try it yourself first