Intermolecular Forces

Front 1

Explain induced dipole-induced dipole forces.

Back 1

They are forces between non-polar molecules.

Front 2

Explain dipole-dipole forces.

Back 2

They are forces between polar molecules.

Front 3

Explain dipole-induced dipole forces.

Back 3

They are forces between polar and non-polar molecules.

Front 4

Briefly explain hydrogen bonding.

Back 4

Hydrogen bonding refers to the forces between molecules in which hydrogen is covalently bonded to nitrogen, oxygen or fluorine. It is a special case of dipole-dipole forces.

Front 5

Give 3 other names for induced dipole-induced dipole forces.

Back 5

London forces

Dispersive forces

Mutually induced dipole forces

Front 6

How are temporary/induced dipoles formed?

Back 6

The electron cloud in one polar molecule is temporarily displaced to one side. The ends of this moleculle will have small charges, and displace electron clouds of adjacent molecules.

Front 7

Name 3 differences between Van der Waals Forces and hydrogen bonding.

Back 7

Front 8

What are the two conditions for hydrogen bonding to occur?

Back 8

Hydrogen must be bonded to a 1) small and 2) highly electronegative atom.

Front 9

Which three elements result in hydrogen bonding when bonded to a hydrogen atom?

Back 9

Oxygen in H2O

Nitrogen in NH3

Fluorine in HF

Front 10

Why is hydrogen bonding such a strong intermolecular force?

Back 10

A large difference in electronegativity results in a significant positive charge on the hydrogen atom. This significant positive charge strongly attracts the highly negative pole (O/N/F) of the adjacent molecule, resulting in a strong intermolecular force. Hydrogen atoms are very small, so the adjacent molecules can approach the original molecule very closely, resulting in a very strong intermolecular force.

Front 11

Why is the boiling point of H2S less that the boiling point of H2O?

Back 11

H2O has hydrogen bonding and H2S has dipole-dipole forces. Hydrogen bonding is stronger then dipole-dipole forces, so it takes more energy to break the hydrogen bonding and cause water to boil.

Front 12

What is the difference between intermolecular and interatomic forces?

Back 12

Intermolecular forces exist between molecular units, whereas interatomic forces exist between atoms in chemical compounds.

Front 13

Show the difference between intermolecular and interatomic forces in a diagram.

Back 13

Front 14

Define: boiling point

Back 14

The temperature at which the vapour pressure of a substance equals atmospheric pressure.

Front 15

What is the relationship between intermolecular forces and boiling point?

Back 15

The stronger the intermolecular forces, the higher the boiling point.

Front 16

Define: melting point

Back 16

The temperature at which the solid and liquid phases of a substance are at equilibrium.

Front 17

Describe the relationship between intermolecular forces and melting point.

Back 17

The stronger the intermolecular forces, the higher the melting point.

Front 18

Define: vapour pressure

Back 18

The pressure exerted by a vapour at equilibrium with its liquid in a closed system.

Front 19

State the relationship between intermolecular forces and vapour pressure.

Back 19

The stronger the intermolecular forces, the lower the vapour pressure.

Front 20

Define: solubility

Back 20

The property of a solid, liquid or gaseous chemical substance (solute) to dissolve in a solid, liquid or gaseous solvent to form a homogeneous solution.