INTERMOLECULAR FORCES

Question 1

What is a dipole-dipole force?

Answer 1

In covalent molecules, polar molecules exert attraction forces called dipole-dipole interactions, the second strongest force

Can exist between the same and different polar molecules, allows molecules to ‘line up’ pull each other in the same way to form stronger surface tension (liquids), it can be manipulated to direct current in the presence of a metal ion

strength of the interaction depends of Zeff, the greater the difference the greater the dipole moment (separation of charges)

Question 2

What is a London dispersion force?

Answer 2

The weakest intermolecular force, exists in all atoms and molecules, caused by temporary dipoles, created by uneven distribution of electrons at any instant

temporary dipole of 1 causes temporary dipole in nearby particle of opposite charge

The only force of attraction between noble gases and non polar molecules

Question 3

What is a hydrogen bond?

Answer 3

Hydrogen bonding is a special type of dipole force, it is the attraction between the H atom of 1 molecule and an O, F, or N of another

The strongest force of the three because Zeff in O, F, N are all higher

Nucleotides in DNA are hydrogen bonded

Question 4

What is an ion-dipole force?

Answer 4

Between an ion and a permanent dipole, when metal salts are dissolved in solutions and hydrates of compounds

Question 5

How is melting point related to attractive forces?

Answer 5

Melting point is lower with the weaker forces (dispersion forces), higher with the higher forces (Hydrogen forces).

Question 6

List, in order, the strongest to weakest forms of bonds

Answer 6

1. Ionic
2. Single covalent
3. Double covalent
4. Triple covalent
5. Hydrogen bonding
6. Dipole-dipole
7. London dispersion