Ethylene glycol is used as an antifreeze in a cold climate. Mass of ethylene glycol which should be added to 4 kg of water to prevent it from freezing at –6°C will be: (Kf for water = 1.86 Kg/mol and molar mass of ethylene glycol = 62 kg/mol)

$∆Tf = kf.m$ 

for ethylene glycol in aq. solution

  $∆Tf = kf \frac{w}{mol.wt} \times \frac{1000}{wt. of solvent}6 = \frac{1.86 x w x 1000}{62 x 4000}$

=> w = 800 g

So, the weight of solute should be more than 800 g.