Question

In a cold climate, water gets frozen causing damage to the radiators of a car. Ethylene glycol is used as an antifreeze agent. The mass of ethylene glycol to be added to 4 kg water to prevent it from freezing at $-6^{o}C.K_f$ for water is $1.85Kmo{l}^{-1}kg$:

• A. $804.32$ g
• B. $635.62$ g
• C. $884.41$ g
• D. None of these

Answer 1

The correct option is A $804.32$ g

Freezing point depression is a colligative property observed in solutions that result from the introduction of solute molecules to a solvent. The freezing points of solutions are lower than that of the pure solvent and is directly proportional to the molality of the solute

$\Delta T_f={T_f}^0-T_f=i.K_b.m$.

Here, $\Delta T_f$ is freezing point depression.

$T_f$ is freezing point of solution.

$K_b$ is depression constant.

Let the mass required be $x$.

Molality ; $m=\frac{\frac{x}{62}}{4}$

$\Delta T_f=0-(-6)=6$

$K_f=1.85$

So,

$6=\frac{x}{248}\times 1.85$

$x=804.38g$

Option A is correct.