Ethylene glycol `("molar mass"=62 g mol^(-1))` is a common automobile antyfreeze. Calculate the freezing point of a solution containing 12.4 g of this substance in 100 g of water. (Given` K_(f) for water = 1.86 K kg mol^(-1))`

Explanation

Moles of ethylene glycol.
` = (12.4)/(62) = 0 . 2` mol
Molality `= (0.2)/(100) xx 1000 = 2 m`
Freezing point depression .
`Delta T_(f) = k_(f) xx m`
` = 1.86 xx 2 = 3.72 k`
Freezing point of aqueous solution
` = 273.15 - 3.72 = 269.43 K`
Boiling point elevation of solution .
`Delta T_(b) = k_(b) xx m`
` = 0.52 xx 2 = 1.04 K`
Boiling point of solution .
` = 373.15 xx 2 = 1.04 K`
Since boiling point is higher than room temperature in summer , it is advisable to keep this substance in the car radiator during summer .