Chapter 13, Problem 13.93P

(a)

Interpretation Introduction

Interpretation:

Whether the solution of $38\text{g}$ of ${\text{C}}_3{\text{H}}_8{\text{O}}_3$ or $38\text{g}$ of ${\text{C}}_2{\text{H}}_6{\text{O}}_2$ has a higher boiling point is to be determined.

Concept introduction:

The boiling point of the substance is the temperature at which the vapor pressure of the liquid becomes equal to the atmospheric pressure and the liquid changes into a vapor. Liquids can change into vapors at temperatures below the boiling point through evaporation. It is the process that occurs on the liquid surface due to which it changes into vapors. Both boiling and freezing points are colligative properties because these depend on the number of moles of solute particles that are present in the substance.

The formula to calculate the change in boiling point is as follows:

$\Delta T_{\text{b}}=i{k}_{\text{b}}m$ (1)

Here, $\Delta T_{\text{b}}$ is the change in boiling point.

$i$ is van’t Hoff factor.

$k_{\text{b}}$ is the boiling point elevation constant.

$m$ is the molality of the solution.

The formula to calculate the molality of the solution is as follows:

$\text{Molality}=\frac{\text{amount}\left(\text{mol}\right)\text{of}\text{solute}}{\text{mass}\left(\text{kg}\right)\text{of}\text{}\text{solvent}}$ (2)

(b)

Interpretation Introduction

Interpretation:

Whether the solution of ${\text{C}}_2{\text{H}}_6{\text{O}}_2$ or $\text{NaCl}$ has a lower freezing point is to be determined.

Concept introduction:

The boiling point of the substance is the temperature at which the vapor pressure of the liquid becomes equal to the atmospheric pressure and the liquid changes into a vapor. Liquids can change into vapors at temperatures below the boiling point through evaporation. It is the process that occurs on the liquid surface due to which it changes into vapors. Both boiling and freezing points are colligative properties because these depend on the number of moles of solute particles that are present in the substance.

The formula to calculate the change in boiling point is as follows:

$\Delta T_{\text{b}}=i{k}_{\text{b}}m$ (1)

Here, $\Delta T_{\text{b}}$ is the change in boiling point.

$i$ is van’t Hoff factor.

$k_{\text{b}}$ is the boiling point elevation constant.

$m$ is the molality of the solution.