Chapter 7, Problem 7.31QP

List the types of intermolecular forces that exist between molecules (or atoms or ions) in each of the following species: (a) benzene (C₆H₆), (b) CH₃Cl, (c) PF₃, (d) NaCl, (e) CS₂.

Interpretation Introduction

Interpretation:

The intermolecular forces presented in the given moleculesbenzene (${\text{C}}_{\text{6}}{\text{H}}_{\text{6}}$), ${\text{CH}}_{\text{3}}\text{Cl}$, ${\text{PF}}_{\text{3}}$, $\text{NaCl}$ and ${\text{CS}}_{\text{2}}$ are to be determined.

Concept introduction:

• Polarity of a bond is due to the difference in electro-negativities of atoms presented in it. The polarities of bonds are represented by using vectors.
• If the result of all bond polarities or vector sum is non-zero in a molecule, then the molecule is called as polar molecule.
• If the result of all bond polarities or vector sum is zero in a molecule, then the molecule is called as nonpolar molecule.
• Intermolecular force is the set of repulsive and attractive forces between molecules that result from the polarity between neighboring molecules. There are four types of intermolecular forces.
• Dipole – Dipole interaction: This force takes place between polar compounds.
• Hydrogen bonding is a type of dipole-dipole interaction of molecules when the hydrogen is bonded to strong electronegative atom (F, O, N, etc) in the molecules.
• Dispersion force is a weak force and this force is present in all compounds force.
• Ionicforces: ions are attracted each otherelectrostatically.

Answer to Problem 7.31QP

Dispersion forces are present inbenzene (${\text{C}}_{\text{6}}{\text{H}}_{\text{6}}$).

Explanation of Solution

To determine: intermolecular forces presented inbenzene (${\text{C}}_{\text{6}}{\text{H}}_{\text{6}}$)..

Dispersion forces are present inbenzene (${\text{C}}_{\text{6}}{\text{H}}_{\text{6}}$).

In the benzene (${\text{C}}_{\text{6}}{\text{H}}_{\text{6}}$) molecule,

There are C-C bonds and C-H bonds presented in benzene (${\text{C}}_{\text{6}}{\text{H}}_{\text{6}}$) molecule. Carbon atom has more electronegativity as compared to hydrogen; so all the C-H bonds in benzene (${\text{C}}_{\text{6}}{\text{H}}_{\text{6}}$) have polarities.

The result of all the bond polarities are the sum of all the vectors associated with each bonds.

The directions of C-H bond vectors are opposite to each other, so they cancel each other.

Hence,

The vector sum or the result of bond polarities for benzene (${\text{C}}_{\text{6}}{\text{H}}_{\text{6}}$) molecule is zero, so benzene (${\text{C}}_{\text{6}}{\text{H}}_{\text{6}}$) is a nonpolar molecule.

Since the benzene (${\text{C}}_{\text{6}}{\text{H}}_{\text{6}}$) is a nonpolar molecule, it exhibit only one type of intermolecular force, which is dispersion forces.

Interpretation Introduction

Interpretation:

The intermolecular forces presented in the given moleculesbenzene (${\text{C}}_{\text{6}}{\text{H}}_{\text{6}}$), ${\text{CH}}_{\text{3}}\text{Cl}$, ${\text{PF}}_{\text{3}}$, $\text{NaCl}$ and ${\text{CS}}_{\text{2}}$ are to be determined.

Concept introduction:

• Polarity of a bond is due to the difference in electro-negativities of atoms presented in it. The polarities of bonds are represented by using vectors.
• If the result of all bond polarities or vector sum is non-zero in a molecule, then the molecule is called as polar molecule.
• If the result of all bond polarities or vector sum is zero in a molecule, then the molecule is called as nonpolar molecule.
• Intermolecular force is the set of repulsive and attractive forces between molecules that result from the polarity between neighboring molecules. There are four types of intermolecular forces.
• Dipole – Dipole interaction: This force takes place between polar compounds.
• Hydrogen bonding is a type of dipole-dipole interaction of molecules when the hydrogen is bonded to strong electronegative atom (F, O, N, etc) in the molecules.
• Dispersion force is a weak force and this force is present in all compounds force.
• Ionicforces: ions are attracted each otherelectrostatically.

Answer to Problem 7.31QP

Dispersion forces and dipole-dipole interaction are present in ${\text{CH}}_{\text{3}}\text{Cl}$.

Explanation of Solution

To determine: intermolecular forces presented in ${\text{CH}}_{\text{3}}\text{Cl}$.

Dispersion forces and dipole-dipole interaction are present in ${\text{CH}}_{\text{3}}\text{Cl}$.

The C-H bond and C-Cl bond in the ${\text{CH}}_{\text{3}}\text{Cl}$ molecule has bond polarity. So ${\text{CH}}_{\text{3}}\text{Cl}$ molecule is a polar molecule.

Polar molecules exhibit dipole-dipole interactions.

Therefore,

Dispersion forces and dipole-dipole interaction are present in ${\text{CH}}_{\text{3}}\text{Cl}$.

Interpretation Introduction

Interpretation:

The intermolecular forces presented in the given molecules benzene (${\text{C}}_{\text{6}}{\text{H}}_{\text{6}}$), ${\text{CH}}_{\text{3}}\text{Cl}$, ${\text{PF}}_{\text{3}}$, $\text{NaCl}$ and ${\text{CS}}_{\text{2}}$ are to be determined.

Concept introduction:

• Polarity of a bond is due to the difference in electro-negativities of atoms presented in it. The polarities of bonds are represented by using vectors.
• If the result of all bond polarities or vector sum is non-zero in a molecule, then the molecule is called as polar molecule.
• If the result of all bond polarities or vector sum is zero in a molecule, then the molecule is called as nonpolar molecule.
• Intermolecular force is the set of repulsive and attractive forces between molecules that result from the polarity between neighboring molecules. There are four types of intermolecular forces.
• Dipole – Dipole interaction: This force takes place between polar compounds.
• Hydrogen bonding is a type of dipole-dipole interaction of molecules when the hydrogen is bonded to strong electronegative atom (F, O, N, etc) in the molecules.
• Dispersion force is a weak force and this force is present in all compounds force.
• Ionicforces: ions are attracted each otherelectrostatically.

Answer to Problem 7.31QP

Dispersion forces and dipole-dipole interaction are present in ${\text{PF}}_{\text{3}}$.

Explanation of Solution

To determine: intermolecular forces presented in ${\text{PF}}_{\text{3}}$.

Dispersion forces and dipole-dipole interaction are present in ${\text{PF}}_{\text{3}}$.

The P-F bond in the ${\text{PF}}_{\text{3}}$ molecule has bond polarity. So ${\text{PF}}_{\text{3}}$ molecule is a polar molecule.

Polar molecules exhibit dipole-dipole interactions.

Therefore,

Dispersion forces and dipole-dipole interaction are present in ${\text{PF}}_{\text{3}}$.

Interpretation Introduction

Interpretation:

The intermolecular forces presented in the given molecules benzene (${\text{C}}_{\text{6}}{\text{H}}_{\text{6}}$), ${\text{CH}}_{\text{3}}\text{Cl}$, ${\text{PF}}_{\text{3}}$, $\text{NaCl}$ and ${\text{CS}}_{\text{2}}$ are to be determined.

Concept introduction:

• Polarity of a bond is due to the difference in electro-negativities of atoms presented in it. The polarities of bonds are represented by using vectors.
• If the result of all bond polarities or vector sum is non-zero in a molecule, then the molecule is called as polar molecule.
• If the result of all bond polarities or vector sum is zero in a molecule, then the molecule is called as nonpolar molecule.
• Intermolecular force is the set of repulsive and attractive forces between molecules that result from the polarity between neighboring molecules. There are four types of intermolecular forces.
• Dipole – Dipole interaction: This force takes place between polar compounds.
• Hydrogen bonding is a type of dipole-dipole interaction of molecules when the hydrogen is bonded to strong electronegative atom (F, O, N, etc) in the molecules.
• Dispersion force is a weak force and this force is present in all compounds force.
• Ionicforces: ions are attracted each otherelectrostatically.

Answer to Problem 7.31QP

Ionic forces are present in $\text{NaCl}$

Explanation of Solution

To determine: intermolecular forces presented in $\text{NaCl}$.

Ionic forces are present in $\text{NaCl}$

$\text{NaCl}$ is an ionic compound, in which ${\text{Na}}^{\text{+}}$ and ${\text{Cl}}^{-}$ ions are electrostatically attracted each other.

Therefore,

Ionic forces are present in $\text{NaCl}$ prevalently.

Interpretation Introduction

Interpretation:

The intermolecular forces presented in the given molecules benzene (${\text{C}}_{\text{6}}{\text{H}}_{\text{6}}$), ${\text{CH}}_{\text{3}}\text{Cl}$, ${\text{PF}}_{\text{3}}$, $\text{NaCl}$ and ${\text{CS}}_{\text{2}}$ are to be determined.

Concept introduction:

• Polarity of a bond is due to the difference in electro-negativities of atoms presented in it. The polarities of bonds are represented by using vectors.
• If the result of all bond polarities or vector sum is non-zero in a molecule, then the molecule is called as polar molecule.
• If the result of all bond polarities or vector sum is zero in a molecule, then the molecule is called as nonpolar molecule.
• Intermolecular force is the set of repulsive and attractive forces between molecules that result from the polarity between neighboring molecules. There are four types of intermolecular forces.
• Dipole – Dipole interaction: This force takes place between polar compounds.
• Hydrogen bonding is a type of dipole-dipole interaction of molecules when the hydrogen is bonded to strong electronegative atom (F, O, N, etc) in the molecules.
• Dispersion force is a weak force and this force is present in all compounds force.
• Ionicforces: ions are attracted each otherelectrostatically.

Answer to Problem 7.31QP

Dispersion forces are present in ${\text{CS}}_{\text{2}}$

Explanation of Solution

To determine: intermolecular forces presented in ${\text{CS}}_{\text{2}}$.

Dispersion forces are present in ${\text{CS}}_{\text{2}}$

In ${\text{CS}}_2$ molecule,

There are two C-S presented in ${\text{CS}}_2$ molecule. Sulfur atom has more electronegativity as compared to carbon atom; so all the bonds in ${\text{CS}}_2$ have polarities.

The result of all the bond polarities are the sum of all the vectors associated with each bonds.

The directions of C-S bond vectors are opposite to each other, so they cancel each other.

Hence,

The vector sum or the result of bond polarities for ${\text{CS}}_2$ molecule is zero, so ${\text{CS}}_2$ is a non-polar molecule.

Therefore,

Only dispersion forces are present in ${\text{CS}}_{\text{2}}$.

Conclusion

Conclusion

The intermolecular forces presented in the given molecules benzene (${\text{C}}_{\text{6}}{\text{H}}_{\text{6}}$), ${\text{CH}}_{\text{3}}\text{Cl}$, ${\text{PF}}_{\text{3}}$, $\text{NaCl}$ and ${\text{CS}}_{\text{2}}$ are determined according to the polarities of molecules.