unit 3: topic 3.1

Question 1

London dispersion forces (weakest)

Answer 1

arises from temporary fluctuating dipoles in molecules

Question 2

what affects London dispersion forces’s strength?

Answer 2

• the more polarizable the molecule, the stronger the LDF will be
• large molecules will have stronger LDF because the increase in electrons increases their polarizability
• long, thin molecules that have more surface area
• double/triple bonds

Question 3

dipole-dipole

Question 4

what are intermolecular forces?

Answer 4

attractions between atoms, ions, molecules that hold them together

Question 5

what are the six types of intermolecular forces? (weakest to strongest?)

Answer 5

1. London dispersion forces
2. dipole-induced dipole force
3. dipole-dipole force
4. hydrogen bonding
5. ion-dipole interactions
6. ion-ion interactions

Question 6

dipole-dipole forces

Answer 6

result from the attraction between the positive end of one dipole and the negative end of another.
- occurs between two polar molecules

Question 7

what affects dipole-dipole strength?

Answer 7

the more polar their molecules, the greater the attraction

Question 8

what is hydrogen bonding with?

Answer 8

• nitrogen
• oxygen
• fluorine

Question 9

hydrogen bonding

Answer 9

occurs between an H atom covalently bonded to a highly electronegative atom (nitrogen, oxygen, fluorine)

Question 10

factors that affect hydrogen bonding strength

Answer 10

• difference in electronegativity creates a large, molecular dipole
• this dipole causes a strong attraction to the dipole on the molecules surrounding it

Question 11

ion-dipole forces (strongest)

Answer 11

present between an ion and a polar molecule

Question 12

what affects the strength of ion-dipole forces: ion charge?

Answer 12

a higher charge on the ion results in a stronger electrostatic attraction with the polar molecule, makes ion-dipole forces stronger

Question 13

what affects the strength of ion-dipole forces: dipole movement

Answer 13

larger dipole movement on the polar molecule indicates a greater separation of change, leading to a stronger interaction with the ion

Question 14

what affects the strength of ion-dipole forces: ion size

Answer 14

smaller ions can get closer to the polar molecule, resulting in stronger ion-dipole forces

Question 15

boiling/freezing/melting: what happens when the IMF increases and why?

Answer 15

increases: stronger IMF: takes more energy (higher temps) to break

Question 16

enthalpy of fusion/vaporization: what happens when the IMF increases and why?

Answer 16

increases: stronger IMF: takes more energy (higher temps) to break