Chapter 16, Problem 17E

(a)

Interpretation Introduction

Interpretation:The molecule with highest boiling point out of ${\text{HBr, Kr or Cl}}_{\text{2}}$ needs to be determined.

Concept Introduction:

Solid state has strong intermolecular force of attraction between particles whereas the gaseous particles have weakest intermolecular forces between particles. Due to intermolecular force of attraction between particles, different interconversions are possible between these three states like evaporation, condensation, sublimation, etc. These states have different intermolecular forces between substances. The intermolecular forces exist between different molecules and are mainly 4 types:

• London dispersion force
• Hydrogen bond
• Dipole-dipole bond
• Ion-dipole bond

The order of strength of forces can be shown as:

London dispersion force < dipole-dipole force < Ion-dipole force

Answer to Problem 17E

  $\text{HBr}$ has highest boiling point compare to ${\text{Kr or Cl}}_{\text{2}}$ .

Explanation of Solution

The ion-dipole and dipole-dipole exist between dipoles and ions whereas hydrogen bonding exist between two electronegative elements whereas H atom acts as bridge. The London dispersion forces exist between two non-polar molecules and are the weakest forces.

As the intermolecular forces become stronger, the boiling point increases because more energy is required to break the forces between molecules. In the given molecules ${\text{Kr \& Cl}}_{\text{2}}$ are non-polar molecules and have weak London dispersion forces whereas $\text{HBr}$ has strong dipole-dipole forces. Thus $\text{HBr}$ has highest boiling point compare to ${\text{Kr or Cl}}_{\text{2}}$ .

(b)

Interpretation Introduction

Interpretation: The molecule with highest freezing point out of ${\text{H}}_{\text{2}}\text{O, NaCl or HF}$ needs to be determined.

Concept Introduction:

Solid state has strong intermolecular force of attraction between particles whereas the gaseous particles have weakest intermolecular forces between particles. Due to intermolecular force of attraction between particles, different interconversions are possible between these three states like evaporation, condensation, sublimation, etc. These states have different intermolecular forces between substances. The intermolecular forces exist between different molecules and are mainly 4 types:

• London dispersion force
• Hydrogen bond
• Dipole-dipole bond
• Ion-dipole bond

The order of strength of forces can be shown as:

London dispersion force < dipole-dipole force < Ion-dipole force

Answer to Problem 17E

  $\text{N}\text{}\text{aCl}$ has highest freezing point compare to ${\text{H}}_{\text{2}}\text{O and HF}$ .

Explanation of Solution

The ion-dipole and dipole-dipole exist between dipoles and ions whereas hydrogen bonding exist between two electronegative elements whereas H atom acts as bridge. The London dispersion forces exist between two non-polar molecules and are the weakest forces.

As the intermolecular forces become stronger, the freezing point increases because more energy is required to melt the forces between molecules.

In the given molecules $\text{N}\text{}\text{aCl}$ is an ionic compound with ionic forces between ions whereas ${\text{H}}_{\text{2}}\text{O and HF}$ have hydrogen bonding. Since ionic bonding is stronger compare to hydrogen bond therefore $\text{N}\text{}\text{aCl}$ has highest freezing point.

(c)

Interpretation Introduction

Interpretation:The molecule with lowest vapor pressure at 25°C of ${\text{Cl}}_{\text{2}}{\text{,Br}}_{\text{2}}{\text{or I}}_{\text{2}}$ needs to be determined.

Concept Introduction:

Solid state has strong intermolecular force of attraction between particles whereas the gaseous particles have weakest intermolecular forces between particles. Due to intermolecular force of attraction between particles, different interconversions are possible between these three states like evaporation, condensation, sublimation, etc. These states have different intermolecular forces between substances. The intermolecular forces exist between different molecules and are mainly 4 types:

• London dispersion force
• Hydrogen bond
• Dipole-dipole bond
• Ion-dipole bond

The order of strength of forces can be shown as:

London dispersion force < dipole-dipole force < Ion-dipole force

Answer to Problem 17E

  ${\text{I}}_{\text{2}}$ has the lowest vapor pressure compare to ${\text{Cl}}_{\text{2}}{\text{,Br}}_{\text{2}}$ molecules.

Explanation of Solution

The ion-dipole and dipole-dipole exist between dipoles and ions whereas hydrogen bonding exist between two electronegative elements whereas H atom acts as bridge. The London dispersion forces exist between two non-polar molecules and are the weakest forces.

All ${\text{Cl}}_{\text{2}}{\text{,Br}}_{\text{2}}{\text{or I}}_{\text{2}}$ molecules are non-polar and have London dispersion forces between molecules. As the molar mass increases, the strength of London dispersion forces also increases that decreases the vapor pressure. Hence ${\text{I}}_{\text{2}}$ has the lowest vapor pressure compare to ${\text{Cl}}_{\text{2}}{\text{,Br}}_{\text{2}}$ molecules.

(d)

Interpretation Introduction

Interpretation:The molecule with lowest freezing point out of ${\text{N}}_{\text{2}}{\text{, CO or CO}}_{\text{2}}$ needs to be determined.

Concept Introduction:

Solid state has strong intermolecular force of attraction between particles whereas the gaseous particles have weakest intermolecular forces between particles. Due to intermolecular force of attraction between particles, different interconversions are possible between these three states like evaporation, condensation, sublimation, etc. These states have different intermolecular forces between substances. The intermolecular forces exist between different molecules and are mainly 4 types:

• London dispersion force
• Hydrogen bond
• Dipole-dipole bond
• Ion-dipole bond

The order of strength of forces can be shown as:

London dispersion force < dipole-dipole force < Ion-dipole force

Answer to Problem 17E

  ${\text{N}}_{\text{2}}$ molecule has lowest freezing point due to lowest molar mass and weakest London forces

Explanation of Solution

The ion-dipole and dipole-dipole exist between dipoles and ions whereas hydrogen bonding exist between two electronegative elements whereas H atom acts as bridge. The London dispersion forces exist between two non-polar molecules and are the weakest forces.

As the intermolecular forces become stronger, the freezing point increases because more energy is required to melt the forces between molecules. In the given molecules ${\text{N}}_{\text{2}}{\text{ \& CO}}_{\text{2}}$ are is are non-polar molecules whereas $\text{CO}$ is a polar molecule. ${\text{N}}_{\text{2}}$ molecule has lowest freezing point due to lowest molar mass and weakest London forcesbecause the strength of London dispersion forces increases with increase in molar mass.

(e)

Interpretation Introduction

Interpretation:The molecule with lowest boiling point out of ${\text{CH}}_{\text{4}}{\text{, CH}}_{\text{3}}{\text{CH}}_{\text{3}}{\text{, CH}}_{\text{3}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{3}}$ needs to be determined.

Concept Introduction:

Solid state has strong intermolecular force of attraction between particles whereas the gaseous particles have weakest intermolecular forces between particles. Due to intermolecular force of attraction between particles, different interconversions are possible between these three states like evaporation, condensation, sublimation, etc. These states have different intermolecular forces between substances. The intermolecular forces exist between different molecules and are mainly 4 types:

• London dispersion force
• Hydrogen bond
• Dipole-dipole bond
• Ion-dipole bond

The order of strength of forces can be shown as:

London dispersion force < dipole-dipole force < Ion-dipole force

Answer to Problem 17E

  ${\text{CH}}_{\text{4}}$ haslowest boiling point compare to ${\text{ CH}}_{\text{3}}{\text{CH}}_{\text{3}}{\text{ or CH}}_{\text{3}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{3}}$ .

Explanation of Solution

The ion-dipole and dipole-dipole exist between dipoles and ions whereas hydrogen bonding exist between two electronegative elements whereas H atom acts as bridge. The London dispersion forces exist between two non-polar molecules and are the weakest forces.

As the intermolecular forces become stronger, the boiling point increases because more energy is required to break the forces between molecules.

In the given molecules, all molecules have London dispersion forces and the strength of force increases with increasing the molar mass. Therefore ${\text{CH}}_{\text{4}}$ has lowest boiling point compare to ${\text{ CH}}_{\text{3}}{\text{CH}}_{\text{3}}{\text{ or CH}}_{\text{3}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{3}}$ .

(f)

Interpretation Introduction

Interpretation:The molecule with highest boiling point out of $\text{HF, HCl, HBr}$ needs to be determined.

Concept Introduction:

Solid state has strong intermolecular force of attraction between particles whereas the gaseous particles have weakest intermolecular forces between particles. Due to intermolecular force of attraction between particles, different interconversions are possible between these three states like evaporation, condensation, sublimation, etc. These states have different intermolecular forces between substances. The intermolecular forces exist between different molecules and are mainly 4 types:

• London dispersion force
• Hydrogen bond
• Dipole-dipole bond
• Ion-dipole bond

The order of strength of forces can be shown as:

London dispersion force < dipole-dipole force < Ion-dipole force

Answer to Problem 17E

  $\text{HF}$ hashighest boiling point compare to $\text{HBr and HCl}$ .

Explanation of Solution

The ion-dipole and dipole-dipole exist between dipoles and ions whereas hydrogen bonding exist between two electronegative elements whereas H atom acts as bridge. The London dispersion forces exist between two non-polar molecules and are the weakest forces.

As the intermolecular forces become stronger, the boiling point increases because more energy is required to break the forces between molecules.

In the given molecules, HF can form hydrogen bonds whereas other two HBr and HCl cannot form hydrogen bond because F is most electronegative. Thus HF has highest boiling point.

(g)

Interpretation Introduction

Interpretation:The molecule with lowest vapor pressure at 25°C of ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{3}}{\text{, CH}}_{\text{3}}{\text{COCH}}_{\text{3}}{\text{, CH}}_{\text{3}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{2}}\text{OH}$ needs to be determined.

Concept Introduction:

Solid state has strong intermolecular force of attraction between particles whereas the gaseous particles have weakest intermolecular forces between particles. Due to intermolecular force of attraction between particles, different interconversions are possible between these three states like evaporation, condensation, sublimation, etc. These states have different intermolecular forces between substances. The intermolecular forces exist between different molecules and are mainly 4 types:

• London dispersion force
• Hydrogen bond
• Dipole-dipole bond
• Ion-dipole bond

The order of strength of forces can be shown as:

London dispersion force < dipole-dipole force < Ion-dipole force

Answer to Problem 17E

  ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{2}}\text{OH}$ has the lowest vapor pressure compare to ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{3}}{\text{, CH}}_{\text{3}}{\text{COCH}}_{\text{3}}$ molecules.

Explanation of Solution

The ion-dipole and dipole-dipole exist between dipoles and ions whereas hydrogen bonding exist between two electronegative elements whereas H atom acts as bridge. The London dispersion forces exist between two non-polar molecules and are the weakest forces.

In the given molecules, ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{3}}{\text{, CH}}_{\text{3}}{\text{COCH}}_{\text{3}}{\text{, CH}}_{\text{3}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{2}}\text{OH}$ , ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{2}}\text{OH}$ has strongest intermolecular force that is hydrogen bond therefore it must have lowest vapor pressure.