Exercise 1 | Colligative Properties of Solutions

Calculate the molality and the mole fractions of a solution prepared by dissolving 23.0 g of fructose, C6H12O6 (s), in 500 mL of water.

Molality m (in mol.kg-1):
 

nsolutemsolution

 

nsolute = msolute / Msolute = msolute / (6 MC + 12 MH + 6 MO)

nsolute = 23.0 / 180.12 = 1.28 x 10-1 mol

msolution = Vsolution x d (with d = density of water = 1.00) = 0.500 kg

 

m = 1.28 × 10-10.5 = 2.55 x 10-1 mol.kg-1

 


Mole Fraction:
 

xsolute = nsolutensolution


nsolute = 23.0 / 180.12 = 1.28 x 10-1 mol

nsolution = 500 / 18.0 = 2.78 x 101 mol
 

xsolute = 1.28 × 10-127.8 = 4.60 x 10-3