Problem: Carbon disulfide (CS2 ) boils at 46.30 oC and has a density of 1.261 g/mL.When 5.40 g of a nondissociating unknown is dissolved in 50.0 mL of CS2, the solution boils at 47.08 oC. What is the molecular weight of the unknown?

FREE Expert Solution

Establish the colligative property for boiling point elevation and determine the molar mass of the unknown solution using the molality calculated


Recall that the boiling point of a solution is higher than that of the pure solvent and the change in boiling point (ΔT­b) is given by:


Tb = Tb solution - Tb pure solvent



The change in boiling point is also related to the molality of the solution:

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Problem Details

Carbon disulfide (CS2 ) boils at 46.30 oC and has a density of 1.261 g/mL.

When 5.40 g of a nondissociating unknown is dissolved in 50.0 mL of CS2, the solution boils at 47.08 oC. What is the molecular weight of the unknown?