In the cryoscopic determination of molar mass, the molar mass in kg mol 1 is given by

In the cryoscopic determination of molar mass, the molar mass in kg mol^ˆ’1is given by

where W is the mass of the solvent, w is the mass of the unknown solute, ΔT_f is the amount by which the freezing point of the solution is less than that of the pure solvent, and K_f and K_f are constants characteristic of the solvent. A sample of an unknown substance was dissolved in benzene, for which K_f = 5.12 K kg mol^ˆ’1 and K_f = 0.011 K^ˆ’1. For the following data, calculate M and its probable error:

W = 13.185 ± 0.003 g,
w = 0.423 ± 0.002 g,
ΔT_f = 1.263 ± 0.020 K.

Transcribed Image Text:

w Kf -(1 – KfATf), WΔT