[VISUAL] | Molecule | Boiling Point of Compound (K) | Dipole Moment (debyes) | Polarizability (10−24 — Intermolecular Forces Chemistry Question
Problem Context
[VISUAL]
| Molecule | Boiling Point of Compound (K) | Dipole Moment (debyes) | Polarizability (10−24 cm3) |
|---|---|---|---|
| HCl | 188 | 1.05 | 2.63 |
| HBr | 207 | 0.80 | 3.61 |
| HI | 238 | 0.38 | 5.44 |
The boiling points, dipole moments, and polarizabilities of three hydrogen halides are given in the table above.
Model Answer
London dispersion forces account for the trend in boiling points. As polarizability of the molecules increases, so does the boiling point of the substance. London dispersion forces depend upon the polarizability of molecules, thus more polarizable molecules have stronger intermolecular forces.
Scoring Guidelines:
- 1 point is earned for identifying London dispersion forces.
- 1 point is earned for explaining the link between polarizability and boiling point.
Model Answer
HF molecules have London dispersion forces and hydrogen bonding. The hydrogen bonding is stronger than both regular dipole-dipole forces and London dispersion forces and accounts for HF’s higher boiling point.
Scoring Guidelines:
- 1 point is earned for a correct explanation.
Model Answer
The drawing in Box 2 should show the undissociated molecules randomly distributed throughout the box.
Scoring Guidelines:
- 1 point is earned for an acceptable diagram.