Intermolecular forces

Question 1

Define Van Der Waals

Answer 1

The attraction between instantaneous and induced dipoles on neighbouring molecules .

Question 2

How does the size of Van Der Waals increase?

Answer 2

The more electrons the greater the Van Der Waals forces.

Question 3

Define permanent Dipole-Dipole forces

Answer 3

Attraction between the positive end, &+, of the permanent dipole on a molecule with the negative end, &-, of the permanent dipole of a neighbouring molecule.

Question 4

Define Hydrogen bond

Answer 4

The attraction between a lone pair pf electrons on a very electronegative atom in one molecule and the hydrogen atom in a neighbouring molecule, in which the hydrogen atom is covalently bonded to a very electronegative atom.

Question 5

Why are the boiling points of H20, HF and NH3 higher than expected?

Answer 5

The are able to form hydrogen bonds between the molecules of the compound.

Question 6

Why does sodium chloride dissolves in water

Answer 6

Sodium chloride is an ionic substance and water is polar - like dissolves like

Question 7

Why do bromine and chlorine mix in hexane?

Answer 7

Bromine, Chlorine and Hexane are all non-polar and like dissolves like.

Question 8

Why does ice have a lower density than water?

Answer 8

The hydrogen bonds in ice are more fixed, which means the water molecules are further apart, leading to a more open structure and a lower density.