Chapter 4.3, Problem 7E

Interpretation Introduction

Interpretation:Higher boiling point of aqueous $\text{NaCl}$ solution as compared to that of pure water should be explained with help of Raoult’s law and Dalton’s law.

Concept introduction:Raoult’s law describes relationship between composition of liquid mixture and vapor pressure. This law holds good only for ideal solutions. Mathematical expression of Raoult’s law is as follows:

  $P_{\text{X}}=P_{\text{X}}^{°}{N}_{\text{X}}$

Where,

• $P_{\text{X}}$ is partial pressure of component $X$ .
• $P_{\text{X}}^{°}$ is partial pressure of pure component $X$ .
• $N_{\text{X}}$ is mole fraction of component $X$ .

Dalton’s law of partial pressures states that total pressure is defined as sum of partial pressure of all volatile components. Mathematical expression for Dalton’s law is as follows:

  $P_{\text{total}}=P_{\text{X}}+P_{\text{Y}}+P_{\text{Z}}+\mathrm{...}$

Where,

• $P_{\text{total}}$is total partial pressure of system.
• $P_{\text{X}}$ is partial pressure of component $X$ .
• $P_{\text{Y}}$ is partial pressure of component $Y$ .
• $P_{\text{Z}}$ is partial pressure of component $Z$ .