Question

Ethylene glycol (C₆H₆O₂) can be used as an antifreeze in the radiator of a car. Calculate the temperature when ice will begin to separate from a mixture with 20 mass percent of glycol in water used in the car radiator. K_f for water = 1.86 K kg mol^-1 and molar mass of ethylene glycol is 62g mol^-1.

Answer 1

Weight of solute (W₂) = 20 mass percent of solution means 20 g of ethylene glycol 

Weight of solvent (water) W₁ = 100 – 20 = 80 g

The temperature at which the ice will begin to separate is the freezing of water after the addition of solute i.e. 7.5 K lower than the normal freezing point of water (273 – 7.5)K = 265.5K