0.24 grams of benzene (C6H6) is dissolved into 4.9 grams of melted biphenyl. The freezing point of the mixture was determined to be 4.4 degrees below the freezing point of pure biphenyl. Based on these results, what is the Kf of biphenyl?

Question

(Use the standard units in your calculation, oC/m, but do not include the units in your answer. Also note these are experimental values so they may not equal the literature value for Kf).

Answer 1

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mol benzene = grams/molar mass benzene. Substitute and solve for mol benzene.

molality = mols benzene/kg biphenyl.
Substitute and solve for molality.

delta T = Kf*m
You know delta T and you know m, solve for Kf.
delta T, of course, is 4.4.
Post your work if you get stuck.