Intermolecular forces

Question 1

What are the three types of intermolecular forces?

Answer 1

1. Van der Waals forces.
   - VdW
   - induced dipole-dipole
   - London forces
   - Dispersion forces
2. Permanent dipole-dipole
3. Hydrogen bonds

Question 2

Explain Van der Waals forces

Answer 2

Electrons in an atom move randomly. Sometimes there are more electrons on one side than the other whch causes the atom to become a temporary dipole. This induces other atoms to become instantaneous dipoles and the bond between these dipole are called the induced dipole-dipole force.

Question 3

What are permanent dipole-dipole forces?

Answer 3

Between oppositely charged sides of dipoles. Due to electronegativity.

Question 4

What is the difference between temporary and permanent dipoles?

Answer 4

Temporary is due to the random movement of electrons whereas, permanent is due to difference in electronegativity of two nuclei.

Question 5

Describe and explain hydrogen bonding

Answer 5

When a hydrogen atom has a covalent bond with another atom with stronger electronegativity, it becomes S+. So it bonds with S- LONE PAIRS from another atom.

Question 6

What conditions must follow for hydrogen bonding to take place?

Answer 6

1. Hydrogen must be S+ as it should be covalently bonded with a more electronegative atom.
2. Must bond with lone pairs

Question 7

Why does water have high MP/BP and why is ice less dense than water?

Answer 7

1. Has a high MP/BP due tot he strong hydrogen bonds.
2. When water is cooled, the water molecules arrange themselves in an ordered structure and the molecules are further apart in ice than in water.