Question

A 0.350g sample of a large biomolecule was dissolved in 15.0g of benzene, and the freezing point depression was determined to be 0.262oC. Calculate the molar mass of the biomolecule.

Answer 1

The molar mass of the biomolecule is 455.73 g/mol

Step-by-step explanation:

∆T = m × Kf

m (molality) = ∆T/Kf

∆T = 0.262 °C, Kf of benzene = 5.12 °C/m

m = 0.262/5.12 = 0.0512 mol/kg

Molecular mass of the biomolecule = mass of biomolecule ÷ (molality × mass of benzene in kilograms) = 0.350 ÷ (0.0512 × 15/1000) = 0.350 ÷ 0.000768 = 455.73 g/mol