Question

Choose the solvent below that would show the greatest freezing point lowering when used to make a 0.20 m nonelectrolyte solution. diethyl ether, kf = 1.79°c/m benzene, kf = 5.12°c/m chloroform, kf = 4.70°c/m ethanol, kf = 1.99°c/m carbon tetrachloride, kf = 29.9°c/m

Answer 1

Answer : Carbon tetrachloride, $k_f=29.9^oC/m$ will show the greatest freezing point lowering.

Explanation :

For non-electrolyte solution, the formula used for lowering in freezing point is,

$\Delta T_f=k_f\times m$

where,

$\Delta T_f$ = lowering in freezing point

$k_f$ = molal depression constant

m = molality

As per question, the molality is same for all the non-electrolyte solution. So, the lowering in freezing point is depend on the $k_f$ only.

That means the higher the value of $k_f$, the higher will be the freezing point lowering.

From the given non-electrolyte solutions, the value of $k_f$ of carbon tetrachloride is higher than the other solutions.

Therefore, Carbon tetrachloride, $k_f=29.9^oC/m$ will show the greatest freezing point lowering.