Pure benzene has a normal freezing point of 5.50 degrees Celsius. A solution containing 11.4 grams of a molecular substance dissolved in 150.0 grams of benzene (Kf=5.12C/m) has a freezing point of 1.20 degrees Celsius. What is the molar mass of the solute?

Answer 1

delta T = Kf*molality.
Solve for molality and substitute in the next equation.

molality = moles/kg solvent. Solve for moles and substitute in the next equation.

moles = grams/molar mass. Solve for molar mass.