Problem:

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?

Strategy:

1. Step 1: Calculate the freezing point depression of the solution.
   
   T_f = (Freezing point of pure solvent) - (Freezing point of solution)
   
   (5.48 ^oC) - (2.07 ^oC) = 3.41 ^oC
   
   
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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