Intermolecular Forces Answers Worksheets 2024 - Free Printable

Explanation:
We are comparing two liquids: benzene (C₆H₆) and phenol (C₆H₅OH). We need to answer 7 questions about their physical properties based on the types of intermolecular forces (IMFs) they have.

Let’s first identify the IMFs present in each:

- Benzene (C₆H₆):
- Nonpolar molecule (symmetrical ring, no significant dipole).
- Only London dispersion forces (LDFs) — weak, temporary dipoles.

- Phenol (C₆H₅OH):
- Has an –OH group attached to the benzene ring.
- The O–H bond is highly polar → allows for hydrogen bonding (a strong type of dipole–dipole force).
- Also has LDFs (all molecules do), and possibly weak dipole–dipole, but H-bonding dominates.

Now answer each question:

1. Which has the stronger IMF?
Phenol has hydrogen bonding; benzene has only LDFs.
→ Phenol has stronger IMFs.

2. Which has the lower vapor pressure?
Stronger IMFs → molecules stick together more → fewer escape into vapor → lower vapor pressure.
→ Phenol has lower vapor pressure.

3. Which has the higher boiling point?
Stronger IMFs require more energy (heat) to break → higher boiling point.
→ Phenol has higher boiling point.

4. Which has the lower viscosity?
Viscosity = resistance to flow. Stronger IMFs → more “stickiness” → higher viscosity.
Benzene (weak LDFs) flows more easily than phenol (H-bonding).
→ Benzene has lower viscosity.

5. Which has the higher surface tension?
Surface tension arises from IMFs pulling molecules inward at the surface. Stronger IMFs → higher surface tension.
→ Phenol has higher surface tension.

6. Which one can H bond?
Hydrogen bonding requires H bonded directly to N, O, or F.
Phenol has O–H → yes. Benzene has only C–H bonds → no H-bonding.
→ Phenol can H bond.

7. Which one has only London dispersion forces?
Benzene is nonpolar and lacks H-bond donors/acceptors → only LDFs.
Phenol has H-bonding, so not *only* LDFs.
→ Benzene has only London dispersion forces.

Let’s double-check:
- All answers align with known data: phenol boils at ~182 °C, benzene at ~80 °C; phenol is more viscous, has higher surface tension, lower vapor pressure — consistent.

Final Answer:
1. Phenol
2. Phenol
3. Phenol
4. Benzene
5. Phenol
6. Phenol
7. Benzene