unit 3

Question 1

intramolecular vs intermolecular

Answer 1

intramolecular = inside a molecule
intermolecular = between molecules

Question 2

intermolecular forces

Answer 2

attractive or repulsive forces between molecules due to differences in charge

Question 3

london dispersion forces

Answer 3

when temporary dipoles form from imbalance of electrons, causing two molecules to become temporarily attracted to each other
- happens to every molecule

Question 4

dipole-dipole forces

Answer 4

attractive forces between + charged end of a POLAR molecule and - charged end of another POLAR molecule
- happens between permanent dipoles

Question 5

hydrogen bonding

Answer 5

only occurs when an H atom bonds with N, O, or F because of the large EN difference
- not actually a bond

Question 6

ion-dipole forces

Answer 6

only occur between an ionic compound and polar molecules because of ions being attracted to the partial charges of the opposing ion (cation or anion)

Question 7

ion-ion attractions

Answer 7

strongest IMF because of the full charges on the ions. creates a crystal lattice with a high melting and boiling point.
- solid sample of an ionic compound

Question 8

when does a molecule have a high boiling point

Answer 8

large molecule (molar mass) + high polarizability + stronger IMF/LDF = higher melting point

Question 9

what is the relationship between noble gases and LDF?

Answer 9

a weak LDF will result in a high vapor pressure

a strong LDF will result in a low vapor pressure

Question 10

when does a molecule have a HIGH boiling point?

Answer 10

if the IMFs are strong, there will be more energy required for vaporization to occur, leading to a high boiling point

Question 11

when does a molecule have a LOW boiling point?

Answer 11

if the IMFs are weak, there will be less energy required for vaporization to occur, leading to a low boiling point

Question 12

define ‘isomer’ and how it differs from resonance structures

Answer 12

molecules with the same chemical formula, but different structures/ configurations

• different from resonance structures/ resonance hybrids because resonance is only concerned with e- arrangement and isomers involve all atoms and e-

Question 13

define ‘normal alkanes’ and its formula

Answer 13

saturated hydrocarbons with a straight, unbranched chain of carbon

formula: CnH2n+2

n= number of carbon atoms in the chain

Question 14

IMFs from weakest to strongest

Answer 14

(weakest) 1. IMF
2. dipole-dipole
3. hydrogen bonding
(strongest) 4. ion-dipole

Question 15

temporary dipole

Answer 15

a dipole that is temporary due to e- imbalances that last for a short amount of time