Understanding Intermolecular and Van der Waals Forces in Chemistry

1. What are the different types of Van Der Waal's forces?

Ionic forces, covalent forces, metallic forces

Dispersion (or London) forces, dipole-dipole forces (including hydrogen bonds), and dipole-induced dipole forces

Van Der Waal's forces are intermolecular forces that encompass dispersion, dipole-dipole, and dipole-induced dipole interactions, not ionic, covalent, or metallic bonds.

Explanation

Van Der Waal's forces are intermolecular forces that encompass dispersion, dipole-dipole, and dipole-induced dipole interactions, not ionic, covalent, or metallic bonds.

2. Which forces are not considered intermolecular forces?

Electrostatic forces (as between ions) or covalent bonds holding a molecule together

London dispersion forces

Van der Waals forces

Hydrogen bonds

Intermolecular forces refer to the forces of attraction or repulsion between molecules. Electrostatic forces and covalent bonds are not considered intermolecular forces because they involve interactions within the molecule itself, rather than between separate molecules. Van der Waals forces, hydrogen bonds, and London dispersion forces are all examples of intermolecular forces that occur between molecules.

Explanation

Intermolecular forces refer to the forces of attraction or repulsion between molecules. Electrostatic forces and covalent bonds are not considered intermolecular forces because they involve interactions within the molecule itself, rather than between separate molecules. Van der Waals forces, hydrogen bonds, and London dispersion forces are all examples of intermolecular forces that occur between molecules.

3. What are van der Waal's forces?

Repulsive intermolecular forces

Covalent bonding between molecules

Ionic bonding between atoms

Attractive intermolecular forces

Van der Waal's forces are weak attractive intermolecular forces that exist between molecules, leading to a variety of physical properties such as boiling points and viscosity in substances.

Explanation

Van der Waal's forces are weak attractive intermolecular forces that exist between molecules, leading to a variety of physical properties such as boiling points and viscosity in substances.

4. What are ion-dipole forces? Are they Van der Waal's forces?

A force between two ions. They are a subset of Van der Waal's forces.

A repulsive force between an ion and a dipole. They are a subset of Van der Waal's forces.

An attractive force between two dipoles. They are a subset of Van der Waal's forces.

Ion-dipole forces are a specific type of intermolecular force, distinct from Van der Waal's forces, which involve interactions between molecules of the same type.

Explanation

Ion-dipole forces are a specific type of intermolecular force, distinct from Van der Waal's forces, which involve interactions between molecules of the same type.

5. Describe, with a diagram, what's a London force?

Forces that repel molecules and atoms from each other.

Permanent dipoles formed in nonpolar molecules or atoms.

Forces that are always repulsive in nature.

London forces, also known as dispersion forces, are temporary attractive forces between molecules or atoms. They arise from the formation of temporary dipoles in nonpolar molecules due to the temporary unsymmetrical electrical charges. These forces are always attractive and help in holding molecules together.

Explanation

London forces, also known as dispersion forces, are temporary attractive forces between molecules or atoms. They arise from the formation of temporary dipoles in nonpolar molecules due to the temporary unsymmetrical electrical charges. These forces are always attractive and help in holding molecules together.

6. What is the range and power of dispersion (London) forces?

Interaction energy proportional to 1/r^4, range ~ 300 pm. Magnitude depends on the atomic number.

Interaction energy proportional to 1/r^6, range ~ 500 pm. Magnitude depends on the polarisability of the atom or molecules.

Interaction energy proportional to 1/r^2, range ~ 200 pm. Magnitude is constant for all atoms.

Interaction energy proportional to 1/r^8, range ~ 600 pm. Magnitude is higher for lighter atoms.

Dispersion (London) forces have a range of approximately 500 pm and their interaction energy is proportional to 1/r^6. The magnitude of these forces depends on the polarisability of the atom or molecule.

Explanation

Dispersion (London) forces have a range of approximately 500 pm and their interaction energy is proportional to 1/r^6. The magnitude of these forces depends on the polarisability of the atom or molecule.

7. Describe, with a diagram, dipole-dipole forces between molecules.

Between molecules with no dipoles. Charges are evenly distributed throughout the molecules.

Between molecules w/ permanent dipole. Partial charges at the ends always less than unit electronic charge.

Between molecules with varying dipole moments. Partial charges at the ends can exceed a unit electronic charge.

Between molecules with temporary dipoles. Partial charges at the ends are equal to a unit electronic charge.

Dipole-dipole forces occur between molecules with permanent dipoles, where partial charges at the ends of the molecules are always less than a unit electronic charge. The incorrect answers provide contrasting scenarios that do not accurately describe dipole-dipole forces.

Explanation

Dipole-dipole forces occur between molecules with permanent dipoles, where partial charges at the ends of the molecules are always less than a unit electronic charge. The incorrect answers provide contrasting scenarios that do not accurately describe dipole-dipole forces.

8. What is the difference in interaction energy of dipole-dipole forces in solids vs liquids?

Solids typically have stationary polar molecules, with i.e. varying 1/r^3, while rotating polar molecules vary 1/r^6.

Solids have weaker dipole-dipole forces compared to liquids.

The interaction energy of dipole-dipole forces is the same in solids and liquids.

Liquids have stationary polar molecules, while solids have rotating polar molecules.

The correct answer highlights that solids and liquids exhibit different behaviors in dipole-dipole forces, with solids having stationary polar molecules leading to interaction energy varying as 1/r^3, while liquids have rotating polar molecules with interaction energy varying as 1/r^6.

Explanation

The correct answer highlights that solids and liquids exhibit different behaviors in dipole-dipole forces, with solids having stationary polar molecules leading to interaction energy varying as 1/r^3, while liquids have rotating polar molecules with interaction energy varying as 1/r^6.

9. Both ICl and Br2 have the same number of atoms and approximately the same molecular weight, but ICl is a solid whereas Br2 is a liquid at 0oC. Why?

The temperature of 0oC has different effects on ICl and Br2 due to their respective boiling points.

ICl and Br2 have different molecular structures, leading to different physical states at 0oC.

Br2 undergoes a phase change at 0oC due to chemical reactions, unlike ICl.

The correct answer relates to the intermolecular forces present in ICl and Br2, specifically focusing on dipole-dipole attractions and nonpolar interactions. Understanding the nature of these forces helps explain why ICl is a solid while Br2 is a liquid at 0oC.

Explanation

The correct answer relates to the intermolecular forces present in ICl and Br2, specifically focusing on dipole-dipole attractions and nonpolar interactions. Understanding the nature of these forces helps explain why ICl is a solid while Br2 is a liquid at 0oC.