Change in freezing point (ΔTf) is given by:
The change in freezing point is also related to the molality of the solution:
i = van’t Hoff factor
m = molality of the solution (in m or mol/kg)
Kf = freezing point depression constant (in ˚C/m)
Recall that the molality of a solution is given by:
ΔTf = 3.66˚C i = 1 (benzene is a non-electrolyte)
m = ?? Kf = 1.86 ˚C • kg/mol (can be found in textbooks or online)
Solving for molality:
= 0.7148 mol compound / kg benzene
A sample of an organic compound (a nonelectrolyte) weighing 1.35 g lowered the freezing point of 10.0 g of benzene by 3.66 °C. Calculate the molar mass of the compound.
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