Question

Retinol is vitamin A and one of the components in multivitamin tablets. A 103.0 mg sample of retinol was dissolved in 1.000 g of chloroform (Kb = 3.630°C/m), increasing the boiling point of chloroform by 1.305°C.

Answer 1

The formula for boiling point elevation is:
deltaT = (Kb)(m), where m is molality of moles solute per kilogram solvent
1.305 = 3.630m
m = 0.3595 = moles/kg solvent
Since we have 1 g of chloroform solvent, this is equivalent to 0.001 kg.
The number of moles is 103 mg or 0.103 g, divided by the molar mass (MM).
0.3595 = (0.103/MM) / 0.001
0.0003595 = 0.103/MM
MM = 286.51 g/mol
Therefore, the molar mass of retinol is 286.51 g/mol