Chapter 16, Problem 18E

(a)

Interpretation Introduction

Interpretation:The molecule with highest boiling point out of ${\text{CCl}}_{\text{4}}{\text{, CF}}_{\text{4}}{\text{, CBr}}_{\text{4}}$ 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 18E

  ${\text{CBr}}_{\text{4}}$ has highest boiling point compare to ${\text{CCl}}_{\text{4}}{\text{ \& CF}}_{\text{4}}$ .

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.

All the given molecules are non-polar due to symmetrical geometry and have London dispersion forces. Since the strength of force increases with increase in molar mass therefore ${\text{CBr}}_{\text{4}}$ has highest boiling point compare to ${\text{CCl}}_{\text{4}}{\text{ \& CF}}_{\text{4}}$ .

(b)

Interpretation Introduction

Interpretation:The molecule with lowest freezing point out of ${\text{F}}_{\text{2}}\text{, LiF or HCl}$ 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 18E

  ${\text{F}}_{\text{2}}$ molecule has lowest freezing point due to lowest molar mass and weakest London dispersion 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, ${\text{F}}_{\text{2}}$ molecules are is are non-polar molecules and have weak London dispersion forces.

LiF is ionic compound and HCl has dipole-dipole interactions thus ${\text{F}}_{\text{2}}$ must have lowest freezing point.

(c)

Interpretation Introduction

Interpretation:The molecule with lowest vapor pressure at 25°C of ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{3}}{\text{, CH}}_{\text{3}}{\text{COCH}}_{\text{3}}{\text{, CH}}_{\text{3}}{\text{CH}}_{\text{2}}\text{OH}$ 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 18E

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

(d)

Interpretation Introduction

Interpretation:The molecule with greatestviscosity out of ${\text{H}}_{\text{2}}{\text{S, HF or H}}_{\text{2}}{\text{O}}_{\text{2}}$ 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 18E

  $\text{HF}$ hasgreatest viscosity compare to ${\text{H}}_{\text{2}}{\text{S and H}}_{\text{2}}{\text{O}}_{\text{2}}$ .

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.

As the strength of intermolecular forces increases, the viscosity increases as the molecules come closer to each other. Since HF molecules have strongest hydrogen bond between molecule compare to ${\text{H}}_{\text{2}}{\text{S and H}}_{\text{2}}{\text{O}}_{\text{2}}$ therefore $\text{HF}$ has greatest viscosity compare to ${\text{H}}_{\text{2}}{\text{S and H}}_{\text{2}}{\text{O}}_{\text{2}}$ .

(e)

Interpretation Introduction

Interpretation:The molecule with greatest heat of vaporization out of ${\text{H}}_{\text{2}}{\text{CO, CH}}_{\text{3}}{\text{CH}}_{\text{3}},{\text{CH}}_{\text{4}}$ 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 18E

In the given molecules, ${\text{H}}_{\text{2}}{\text{CO, CH}}_{\text{3}}{\text{CH}}_{\text{3}},{\text{CH}}_{\text{4}}$ , ${\text{H}}_{\text{2}}\text{CO}$ has strongest dipole-dipole interactions therefore it should have highest enthalpy of vaporization.

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.

The enthalpy of vaporization also increases with increase in molar mass and strength intermolecular forces. In the given molecules, ${\text{H}}_{\text{2}}{\text{CO, CH}}_{\text{3}}{\text{CH}}_{\text{3}},{\text{CH}}_{\text{4}}$ , ${\text{H}}_{\text{2}}\text{CO}$ has strongest dipole-dipole interactions therefore it should have highest enthalpy of vaporization.

(f)

Interpretation Introduction

Interpretation:The molecule with smallest enthalpy of fusion out of ${\text{I}}_{\text{2}}\text{, CsBr,CaO}$ 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 18E

In the given molecules, ${\text{I}}_{\text{2}}\text{, CsBr,CaO}$ , ${\text{I}}_{\text{2}}$ has weakest London dispersion forces therefore it should have smallest enthalpy of fusion.

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.

The enthalpy of fusion also increases with increase in molar mass and strength intermolecular forces. In the given molecules, ${\text{I}}_{\text{2}}\text{, CsBr,CaO}$ , ${\text{I}}_{\text{2}}$ has weakest London dispersion forces therefore it should have smallest enthalpy of fusion.