Question

Ethylene glycol (molar mass = 62 g/mol) is a common automobile antifreeze. Calculate the freezing point of a solution containing 12.4g of this substance in 100 g of water. Would it be advisable to keep this substance in the car radiator during summer? Given : kf for water = 1.86k kg/mol, kb for water = 0.512k kg/mol

Answer 1

Concept:

Depression in freezing point due to any solute is known as colligative property

$ΔT_{f} = K_{f}*m$

Here, m is molality that is equal to moles of solute in per kg solvent.

Explanation:

Moles of ethylene glycol = $\frac{12.4}{62} = 0.2$

Molality $m = \frac{0.2}{0.1} =  2$

On substituting above values in depression in freezing point expression

We get,

$ΔT_{f} = 1.86*2 =  3.72 K$

Reason: Ethylene glycol added into water in summer because it reduced the freezing point of water and act as anti-freezing agent so that in summer it  reduced the boiling of water in car radiator.

Conclusion:

The depression in freezing point = 3.71 K