Question

0.075 molal solution of sucrose solution contain 1kg water is at temperature of -0.4 degree Celsius , If (K f )H2O = 1.86 How much ice will freeze out ?

Answer 1

Answer:

Molar mass of sucrose= 342gmol

−1

So mass of sucrose per kg of solvent= 0.75×342=256.5g

Mass of sucrose in 1kg of solution=

1000+256.5

256.5

×1000=204.14g

Mass of solvent= 1000−204.14=795.86g

ΔT

f

=iK

f

×m=1×1.86×

342

204.14

×

W

1000

⇒4=

342×W

1.86×204.14×1000

⇒W=277.55g

Amount of ice will be separated= 795.86−277.55=518.31g .