Chapter 12, Problem 1E

For each of the following substances describe the importance of dispersion (London) forces, dipole-dipole interactions, and hydrogen bonding:

(a)HCl; (b) ${\text{Br}}_{\text{2}}$ ; (c) ICI; (d) HF; (e) ${\text{CH}}_{\text{4}}$ .

Interpretation Introduction

(a)

Interpretation:

Importance of dispersion forces, dipole-dipole interactions and hydrogen bonding for HCl should be described.

Concept introduction:

There are two kind of forces act on molecules. One is intramolecular forces and the other one is intermolecular forces. Intramolecular forces are forces that can be seen within atoms of a molecule. Intermolecular forces exist between the two molecules of same type. Types of intermolecular forces are dipole-dipole interactions, dipole-induced dipole interactions and dispersion interactions. Dipole-dipole interactions occur between the molecules which are polarized with partial positive charge and partial negative charge. Hydrogen bonding is also a special kind of dipole-dipole interaction which forms between H atoms and oxygen, nitrogen or fluorine atoms. Dipole-induced dipole arises by inducing a change in dipole moment of neighboring molecule by a dipole moment of one molecule. Dispersion interactions is occurred by instantaneous dipoles resulted from asymmetric distribution of electrons within a molecule during constant motion of electrons.

Answer to Problem 1E

There are dipole-dipole interactions and dispersion forces between HCl molecules.

Explanation of Solution

HCl is a polar moleculebecause electronegativities of H and Cl are significantly different. Therefore, major intermolecular force present is dipole-dipole interactions. The dispersion forces are also present. There is no hydrogen bonding between HCl molecules as electronegativity of Cl is not sufficient to form hydrogen bonds.

Interpretation Introduction

(b)

Interpretation:

Importance of dispersion forces, dipole-dipole interactions and hydrogen bonding for Br₂ should be described.

Concept introduction:

There are two kind of forces act on molecules. One is intramolecular forces and the other one is intermolecular forces. Intramolecular forces are forces that can be seen within atoms of a molecule. Intermolecular forces exist between the two molecules of same type. Types of intermolecular forces are dipole-dipole interactions, dipole-induced dipole interactions and dispersion interactions. Dipole-dipole interactions occur between the molecules which are polarized with partial positive charge and partial negative charge. Hydrogen bonding is also a special kind of dipole-dipole interaction which forms between H atoms and oxygen, nitrogen or fluorine atoms. Dipole-induced dipole arises by inducing a change in dipole moment of neighboring molecule by a dipole moment of one molecule. Dispersion interactions is occurred by instantaneous dipoles resulted from asymmetric distribution of electrons within a molecule during constant motion of electrons.

Answer to Problem 1E

Only dispersion forces are present in Br₂

Explanation of Solution

Br₂ is a non-polar molecule therefore, it does not have permanent dipoles. No dipole-dipole interactions are present. But it can induce instantaneous dipoles and make dispersion forces. Br₂ cannot formhydrogen bonding as there is no H atom present.

Interpretation Introduction

(c)

Interpretation:

Importance of dispersion forces, dipole-dipole interactions and hydrogen bonding for ICl should be described.

Concept introduction:

There are two kind of forces act on molecules. One is intramolecular forces and the other one is intermolecular forces. Intramolecular forces are forces that can be seen within atoms of a molecule. Intermolecular forces exist between the two molecules of same type. Types of intermolecular forces are dipole-dipole interactions, dipole-induced dipole interactions and dispersion interactions. Dipole-dipole interactions occur between the molecules which are polarized with partial positive charge and partial negative charge. Hydrogen bonding is also a special kind of dipole-dipole interaction which forms between H atoms and oxygen, nitrogen or fluorine atoms. Dipole-induced dipole arises by inducing a change in dipole moment of neighboring molecule by a dipole moment of one molecule. Dispersion interactions is occurred by instantaneous dipoles resulted from asymmetric distribution of electrons within a molecule during constant motion of electrons.

Answer to Problem 1E

Dipole-dipole interactions and dispersion forces are present in ICl

Explanation of Solution

ICl is a polar molecule because electronegativities of I and Cl are significantly different. Therefore major intermolecular force present is dipole-dipole interactions. And dispersion forces are also present. There is no hydrogen bonding between ICl molecules due to absence of H atoms.

Interpretation Introduction

(d)

Interpretation:

Importance of dispersion forces, dipole-dipole interactions and hydrogen bonding for HF should be described.

Concept introduction:

There are two kind of forces act on molecules. One is intramolecular forces and the other one is intermolecular forces. Intramolecular forces are forces that can be seen within atoms of a molecule. Intermolecular forces exist between the two molecules of same type. Types of intermolecular forces are dipole-dipole interactions, dipole-induced dipole interactions and dispersion interactions. Dipole-dipole interactions occur between the molecules which are polarized with partial positive charge and partial negative charge. Hydrogen bonding is also a special kind of dipole-dipole interaction which forms between H atoms and oxygen, nitrogen or fluorine atoms. Dipole-induced dipole arises by inducing a change in dipole moment of neighboring molecule by a dipole moment of one molecule. Dispersion interactions is occurred by instantaneous dipoles resulted from asymmetric distribution of electrons within a molecule during constant motion of electrons.

Answer to Problem 1E

Dispersion forces, dipole-dipole interactions and hydrogen bonding are present in HF.

Explanation of Solution

HF is a polar molecule as the electronegativities of H and F are significantly different. Therefore dipole-dipole interactions are present and dispersion forces also can be seen. HF can form hydrogen bonds as H in one HF molecule can interact with F atom in another HF molecule due to electronegativity difference between H and F.

Interpretation Introduction

(e)

Interpretation:

Importance of dispersion forces, dipole-dipole interactions and hydrogen bonding for CH₄ should be described.

Concept introduction:

There are two kind of forces act on molecules. One is intramolecular forces and the other one is intermolecular forces. Intramolecular forces are forces that can be seen within atoms of a molecule. Intermolecular forces exist between the two molecules of same type. Types of intermolecular forces are dipole-dipole interactions, dipole-induced dipole interactions and dispersion interactions. Dipole-dipole interactions occur between the molecules which are polarized with partial positive charge and partial negative charge. Hydrogen bonding is also a special kind of dipole-dipole interaction which forms between H atoms and oxygen, nitrogen or fluorine atoms. Dipole-induced dipole arises by inducing a change in dipole moment of neighboring molecule by a dipole moment of one molecule. Dispersion interactions is occurred by instantaneous dipoles resulted from asymmetric distribution of electrons within a molecule during constant motion of electrons.

Answer to Problem 1E

Dispersion forces are present in CH₄.

Explanation of Solution

CH₄ is a non-polar molecule so, it does not have permanent dipoles. Thus, no dipole-dipole interactions present. But it can induce instantaneous dipoles leading to dispersion forces. CH₄ cannot form hydrogen bonds.