Question

Name the compound given below, having the highest freezing point.
A) 1m NaCl solution.
B) 1m KCL solution.
C) 1m $AlC{l_3}\,\,solution.$
D) 1m ${C_6}{H_{12}}{O_{6\,}}\,\,$

Answer 1

First of all we should know about the freezing point for solving this question. Hence, freezing point is the temperature at which a liquid is transformed into solid. Freezing point generally increases with the increase in melting point.

Complete answer:
Molecules having the stronger intermolecular forces are generally pulled together tightly so as to form a solid at higher temperatures, hence their freezing point is generally higher. The molecules which have the lower intermolecular forces will not change into solid till the temperature is further lowered.
The normal freezing point at which a substance melts is 760 mm of Hg.
Freezing point is generally a part of colligative property. The colligative properties are the properties which generally depend upon the concentration of ions or solute molecules. They are independent of the identity of the solute.
The depression in freezing point is generally calculated by the formula -
$\Delta {T_s} = i \times {K_f} \times m$
Here, it is the Van't Hoff factor, which depends on the degree of association/dissociation of solute in the solution and the number of ions which are produced in the solution.
Since, $\alpha = \dfrac{{i - 1}}{{n - 1}}$
Thus, greater the value of n, lower is Van’t Hoff factor.
For NaCl, n=2
For KCl, n=2
For$AlC{l_3}\,\,$ n=4
For${C_6}{H_{12}}{O_{6\,}}\,\,$ ,n=1
Hence, the lower the Van’t Hoff factor results in the least depression in freezing point. Thus, the solution has the highest freezing point.
Hence, the option D, is correct.

Note: For certain organic compound’s case such as fats freezing point is generally lower than the melting point. Generally, the freezing point for any substance is 1. Generally, a solution has lower freezing point than that of a pure solvent.