Solutions

Solutions

Question

A 10% solution (by mass) of sucrose in water has the freezing point of 269.15 K.Calculate the freezing point of 10% glucose in water if freezing point of pure water is273.15 K.

Given : (Molar mass of sucrose = 342 g mol–1) (Molar mass of glucose = 180 g mol–1)

Answer

Given,
T1=269.15 K
T2 = 273.15
Molar mass of sucrose = 342 g mol–1
Molar mass of glucose = 180 g mol–1
ΔTf = Kf m
Here , m = w2x 1000/ M2XM1
273.15-269.15 = Kf x 10 x1000/ 342 x90
Kf = 12.3 K kg/mol
ΔTf = Kf m
= 12.3 x 10 x1000/ 180x90
= 7.6 K
Tf = 273.15 – 7.6 = 265.55 K

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