Chapter 10, Problem 10.37SP

(a)

Interpretation Introduction

Interpretation:

The largest dispersion force among Ethane and octane has to be given.

Concept Introduction:

Intermolecular forces:

Intermolecular forces are like cohesive forces, acting between the molecules.  The overall stability of a compound depends on how strong the molecules are held together. Intermolecular force is concerned about the overall stability of a substance.  A stable substance has stronger intermolecular forces.

London dispersion force:

London dispersion forces exist in non-polar compounds whereas dipole-dipole forces exist in polar covalent compounds.  Dipole-dipole force is stronger than London dispersion force.  Both polar and non-polar covalent compounds have London dispersion forces.  These forces are due to temporary dipoles and do not exist permanently.  The molecules convert to dipoles instantly and disappear.  This is due to the uneven distribution of electrons between their atoms occurs momentarily when the bonded electrons approach nucleus.  Thus it is a weakest force.

Larger size molecules have lesser interaction between nuclei and electrons.  Thus the electrons are free from nuclear force of attraction and easily form dipoles.  Thus, larger the size of the molecules, higher is the strength of London dispersion force.

(b)

Interpretation Introduction

Interpretation:

The largest dispersion force among $\text{HCl and HI}$ has to be given.

Concept Introduction:

Intermolecular forces:

Intermolecular forces are like cohesive forces, acting between the molecules.  The overall stability of a compound depends on how strong the molecules are held together. Intermolecular force is concerned about the overall stability of a substance.  A stable substance has stronger intermolecular forces.

London dispersion force:

London dispersion forces exist in non-polar compounds whereas dipole-dipole forces exist in polar covalent compounds.  Dipole-dipole force is stronger than London dispersion force.  Both polar and non-polar covalent compounds have London dispersion forces.  These forces are due to temporary dipoles and do not exist permanently.  The molecules convert to dipoles instantly and disappear.  This is due to the uneven distribution of electrons between their atoms occurs momentarily when the bonded electrons approach nucleus.  Thus it is a weakest force.

Larger size molecules have lesser interaction between nuclei and electrons.  Thus the electrons are free from nuclear force of attraction and easily form dipoles.  Thus, larger the size of the molecules, higher is the strength of London dispersion force.

(d)

Interpretation Introduction

Interpretation:

The largest dispersion force among ${\text{H}}_{\text{2}}{\text{O and H}}_{\text{2}}\text{Se}$ has to be given.

Concept Introduction:

Intermolecular forces:

Intermolecular forces are like cohesive forces, acting between the molecules.  The overall stability of a compound depends on how strong the molecules are held together. Intermolecular force is concerned about the overall stability of a substance.  A stable substance has stronger intermolecular forces.

London dispersion force:

London dispersion forces exist in non-polar compounds whereas dipole-dipole forces exist in polar covalent compounds.  Dipole-dipole force is stronger than London dispersion force.  Both polar and non-polar covalent compounds have London dispersion forces.  These forces are due to temporary dipoles and do not exist permanently.  The molecules convert to dipoles instantly and disappear.  This is due to the uneven distribution of electrons between their atoms occurs momentarily when the bonded electrons approach nucleus.  Thus it is a weakest force.

Larger size molecules have lesser interaction between nuclei and electrons.  Thus the electrons are free from nuclear force of attraction and easily form dipoles.  Thus, larger the size of the molecules, higher is the strength of London dispersion force.