Chapter 16, Problem 65A

(a)

Interpretation Introduction

Interpretation: The solution that has the higher boiling point is to be determined between seawater and distilled water.

Concept Introduction: The temperature at which the pressure applied on a liquid is equal to the pressure exerted by the vapour of liquid is known as boiling point. In simple words, it can be defined as ‘The point of temperature at which the liquid starts to boil.’

Every liquid has its unique boiling point.

Answer to Problem 65A

The boiling point of the seawater is greater than the distilled water.

Explanation of Solution

Distilled water has very fewer mineral impurities so the water can be expected to boil at exact $100°\text{C}$ . The increase in boiling point also differs depending on the surrounding environmental pressure. The liquid at partial vacuum has a lower boiling point compared to liquid at atmospheric pressure. Seawater is exposed to atmospheric pressure and has a higher boiling point compared to distilled water.

(b)

Interpretation Introduction

Interpretation: The solution that has the higher boiling point is to be determined between $1\cdot 0M{\text{KNO}}_3$ and $1\cdot 5M{\text{KNO}}_{\text{3}}$ .

Concept Introduction:

Molarity of a solution is defined as moles of solute by the litre of solution. Higher the molarity of the solution higher is the boiling point.

Answer to Problem 65A

The boiling point of $1\cdot 5M{\text{KNO}}_{\text{3}}$ is greater than $1\cdot 0M{\text{KNO}}_3$ .

Explanation of Solution

While heating a solution, the dissolved solute is mixed with the solvent molecules at the surface where heat/boiling occurs. The higher concentration of solute will take more time and temperature to dissolve the solute and start boiling. Therefore, compound with high molarity value has the higher boiling point. Hence, boiling point of $1\cdot 5M{\text{KNO}}_{\text{3}}$ is greater than $1\cdot 0M{\text{KNO}}_3$ .

(c)

Interpretation Introduction

Interpretation: The solution that has the higher boiling point is to be determined between $0\cdot 100M\text{KCl}$ and $0\cdot 100M{\text{MgCl}}_{\text{2}}$ .

Concept Introduction: The boiling point of the compound depends on the molecular mass as well. The higher molecular mass the greater is the boiling point.

Answer to Problem 65A

The boiling point of $0\cdot 100M{\text{MgCl}}_{\text{2}}$ is greater than $0\cdot 100M\text{KCl}$ .

Explanation of Solution

If the mass of a compound is higher it requires higher temperature for the solute to dissolve in the solvent and start boiling. Therefore, the molecular mass of $0\cdot 100M{\text{MgCl}}_{\text{2}}$ is $95.21\text{g/mol}$ which is greater than mass of $0\cdot 100M\text{KCl}$ which is $\text{74}\text{.55}\text{g/mol}$ .