Answer:
124.6 g/mol will be the molar mass for the unknown non-electrolyte
Explanation:
Freezing point depression → ΔT = Kf . m
ΔT indicates the temperature variation:
Freezing point of pure solvent - Freezing point of solution
Kf is the cryoscopic constant → 29.8 K/m
Generally the unit is °C/m but we have to type the ΔT by K so let's replace the data given → 7.03 K = 29.8 K/m . m
m = 7.03 K / 29.8 m/K = 0.236 mol/kg
m means molality, the moles of solute in 1 kg of solvent. If we want to determine the moles of solute we do this operation:
molality . kg, so we may convert the mass of solvent from g to kg.
50 g . 1kg/1000g = 0.05 kg
0.236 mol/kg . 0.05 kg = 0.0118 moles
Molar mass → g/mol → So 1.47 g / 0.0118 mol = 124.6 g/mol
