Chapter 16, Problem 12STP

Interpretation Introduction

Interpretation : The relationship between molarity and freezing point depression is to be outlined.

Concept Introduction : Molarity mainly explains the concentration of a solute and the freezing point depression is a colligative property that depends on the number of solute particles and it increases with an increase in the concentration of solute Molarity is the ratio of moles of a solute to the volume of solution in liter. Molarity is the ratio of moles of a solute to the volume of solution in a liter. It is denoted by $\text{M}$ .

The expression for molarity is as follows:

  $\text{M}=\frac{\text{moles of solute}}{\text{Volume of solution(L)}}$

Answer to Problem 12STP

The Freezing point depression is a colligative property that depends on the number of solute particles and it increases with an increase in the concentration of solute as the more the solute more it will alter the freezing point of the solvent or solution.

Explanation of Solution

Molarity mainly explains the concentration of a solute and the freezing point depression is a colligative property that depends on the number of solute particles it increases with an increase in the concentration of solute as the more the solute more it will alter the freezing point of the solvent or solution. Also from the graph, it is clear that freezing point depression increases with an increase in molarity.

The data is given as:

Molarity	Freezing point depression
	$\text{NaCl}$	${\text{CaCl}}_2$	${\text{C}}_2{H}_{6}O$
$0.5$	$1.7$	$2.6$	$0.95$
$1.0$	$3.5$	$5.6$	$2.0$
$1.5$	$5.3$	$8.3$	$3.0$
$2.0$	$7.2$	$11.2$	$4.1$
$2.5$	$9.4$	$14.0$	$5.3$

The required graph is plotted as:

  

Hence, the freezing point depression increases with an increase in molarity.

Conclusion

The freezing point depression of a solute increases with an increase in molarity.