AP Chemistry: Intermolecular Forces & Properties 2 — Questions and Answers
Question 1: Which intermolecular force is responsible for the unusually high boiling point of water compared to H2S?
- Hydrogen bonding (Correct answer)
- London dispersion forces
- Ion-dipole forces
- Covalent bonding
Correct answer: Hydrogen bonding
Water's O-H bonds enable strong hydrogen bonding, which H2S lacks because sulfur is less electronegative.
Question 2: Which molecule exhibits ONLY London dispersion forces?
- CH4 (Correct answer)
- NH3
- H2O
- HCl
Correct answer: CH4
CH4 is nonpolar, so only temporary dipole London dispersion forces operate.
Question 3: As molar mass increases among nonpolar molecules, London dispersion forces generally:
- Increase (Correct answer)
- Decrease
- Stay constant
- Disappear
Correct answer: Increase
Larger molecules have more electrons and greater polarizability, strengthening dispersion forces.
Question 4: Which pair of molecules can form hydrogen bonds with each other?
- NH3 and H2O (Correct answer)
- CH4 and CO2
- CH4 and CCl4
- Cl2 and Br2
Correct answer: NH3 and H2O
Both NH3 and H2O have H bonded to N or O, allowing hydrogen bonding between them.
Question 5: Dipole-dipole forces occur between molecules that are:
- Polar (Correct answer)
- Nonpolar
- Monatomic
- Ionic only
Correct answer: Polar
Permanent dipoles in polar molecules attract one another via dipole-dipole forces.
Question 6: Which has the strongest intermolecular forces at room temperature?
- Liquid water (Correct answer)
- Helium gas
- Neon gas
- Methane gas
Correct answer: Liquid water
Water is liquid at room temperature due to strong hydrogen bonding, while the others are gases.
Question 7: Ion-dipole forces are most important in which situation?
- Dissolving NaCl in water (Correct answer)
- Boiling pure nitrogen
- Melting solid iodine
- Subliming dry ice
Correct answer: Dissolving NaCl in water
When NaCl dissolves, water dipoles surround Na+ and Cl- ions via ion-dipole attractions.
AP Chemistry: Intermolecular Forces & Properties 2
Which intermolecular force is responsible for the unusually high boiling point of water compared to H2S?