The boiling point of a solution containing 5.35 g of a nonvolatile hydrocarbon in 102.2
g of acetone is 56.60°C. What is the molecular weight of the hydrocarbon?
For acetone, Tb = 55.95°C and Kb = 1.71 °C/m

Respuesta :

The molar mass of the hydrocarbon is 138 g/mol.

We know that;

ΔT = K  m i

K = boiling constant of acetone

m = molality of the solution

i = Van't Hoff factor

ΔT =  56.60°C - 55.95°C = 0.65°C

m = ΔT/K i

m = 0.65°C/1.71 °C/m × 1

m = 0.38 m

Now;

m = Number of moles of solute/ mass of solvent in kilograms

0.38 = 5.35/MM/0.1022

0.38 = 5.35/MM × 0.1022

0.38 × MM × 0.1022 = 5.35

MM =  5.35/0.38 ×  0.1022

MM = 138 g/mol

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