Calculation of Molecular Weight from Freezing Point Depression Data


The freezing point of a solution that contains 1.00 g of an unknown compound, (A), dissolved in 10.0 g of benzene is found to be 2.07 oC. The freezing point of pure benzene is 5.48 oC. The molal freezing point depression constant of benzene is 5.12 oC/molal. What is the molecular weight of the unknown compound?


  1. Step 1: Calculate the freezing point depression of the solution.

  2. Step 2 : Calculate the molal concentration of the solution using the freezing point depression.

  3. Step 3: Calculate the molecular weight of the unknown using the molal concentration.

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