AP Chemistry: Intermolecular Forces & Properties 3 — Questions and Answers
Question 1: Which property of water is a direct consequence of hydrogen bonding?
- High surface tension (Correct answer)
- Low boiling point
- Low specific heat
- Poor solvent ability
Correct answer: High surface tension
Hydrogen bonds pull surface molecules together, producing high surface tension.
Question 2: Why is ice less dense than liquid water?
- Hydrogen bonds form an open crystal lattice (Correct answer)
- Ice has fewer molecules
- Water expands when heated
- Ice contains trapped air
Correct answer: Hydrogen bonds form an open crystal lattice
Hydrogen bonding arranges water molecules into an open hexagonal lattice with more empty space.
Question 3: A liquid with a high vapor pressure at room temperature most likely has:
- Weak intermolecular forces (Correct answer)
- Strong hydrogen bonding
- High molar mass
- Strong ion-dipole forces
Correct answer: Weak intermolecular forces
Weak intermolecular forces let molecules escape easily, raising vapor pressure.
Question 4: Which substance is expected to have the highest boiling point?
- C5H12 (pentane) (Correct answer)
- C3H8 (propane)
- C2H6 (ethane)
- CH4 (methane)
Correct answer: C5H12 (pentane)
Pentane has the largest molar mass and most electrons, giving the strongest dispersion forces.
Question 5: Capillary action of water in a thin glass tube results from:
- Adhesion and cohesion (Correct answer)
- Only London forces
- Ionic bonding
- Covalent network bonding
Correct answer: Adhesion and cohesion
Adhesion to glass and cohesion among water molecules together drive capillary rise.
Question 6: Compared to a branched isomer, a straight-chain alkane usually has a higher boiling point because it has:
- Greater surface contact for dispersion forces (Correct answer)
- Stronger hydrogen bonds
- More ionic character
- Higher molar mass
Correct answer: Greater surface contact for dispersion forces
Straight chains contact each other over more surface area, strengthening London dispersion forces.
Question 7: Water's high specific heat capacity is largely due to:
- Energy needed to break hydrogen bonds (Correct answer)
- Its low molar mass
- Strong covalent O-H bonds
- London dispersion forces
Correct answer: Energy needed to break hydrogen bonds
Much absorbed heat goes into disrupting hydrogen bonds rather than raising temperature.
AP Chemistry: Intermolecular Forces & Properties 3
Which property of water is a direct consequence of hydrogen bonding?