75g of ethylene glycol is dissolved in 500g water. The solution is placed in a refrigerator maintained at a temperature of 263.7K. What amount of ice will separate out at this temperature.
(Kf water = 1.86 K/m)

1) 300g
2) 200g
3) 178g
4) 258g

1) Depression in freezing point, ΔTf = Tf(freezing point of the pure solvent) - Tf (freesing point when non-volatile solute is dissolved in it) = 273 - 263.7 K = 9.3 K

2) Now, we have to calculate the weight of the solvent i.e. water, W, which is equal to


where, w and m are the weight and molar mass of the solute i.e ethylene glycol. kf is given.

So, W=1.86 ×75×100062×9.3=242 g

Hence the amount of ice which will separate out from 500 g of water will be = 500 - 242 = 258 g.

Hence option 4 is correct.

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