Unit 3: Intermolecular Forces and Properties
Chemistry · Unit 3 · Paper 2

Intermolecular Forces and Properties unit test

A test on this unit alone, marked as a percentage and a letter grade — for the test your class is actually sitting, rather than for May. Answer everything, then submit once: seeing the answer to question 3 before attempting question 4 makes the final percentage meaningless.

Paper 1Paper 2Paper 3
Each paper is built from this unit’s 22 terms and is the same for everyone, so a teacher can assign “Unit 3, Paper 2” and every student sits the identical test. Multiple choice is marked objectively; the written sections you mark yourself against the model answer and rubric.
Suggested time 31 min 28 points0/17 attempted
1

London dispersion forces

2

Vapor pressure

3

Why intermolecular forces are weaker than bonds

4

Hydrogen bonding

5

Capillary action

6

Real gas deviation direction

7

Maxwell-Boltzmann distribution

8

Distillation

9

Boiling point and IMF strength

10

Ion-dipole forces

11

Comparing boiling points correctly

12

Molarity

Short answer 1. Define or explain: Partial pressure and Dalton's law

3 pts

Short answer 2. Define or explain: Kinetic molecular theory assumptions

3 pts

Short answer 3. Define or explain: Beer-Lambert law

3 pts

Short answer 4. Define or explain: Solubility and "like dissolves like"

3 pts

Free response

4 pts

A scientist is investigating the properties of a mixture of CH3OH and H2CO. A diagram represents the mixture: several methanol molecules (a carbon bonded to three hydrogens and to an —OH group) and several formaldehyde molecules (a carbon double-bonded to an oxygen and single-bonded to two hydrogens), drawn side by side with no interactions marked. The scientist plans to cool a gaseous mixture of CH3OH and H2CO to form a liquid mixture, and finds the following data. Substance Melting point (K) Boiling point (K) Enthalpy of vaporization (kJ/mol) CH3OH 176 338 37.6 H2CO 181 254 24.2 The molar mass of CH3OH is 32.04 g/mol.

(a) Identify the hybridization of the valence orbitals of the C atom in the H2CO molecule.

(b) The released exam asks the student to draw a single dashed line representing a strong hydrogen-bonding attraction between one CH3OH molecule and one H2CO molecule in the mixture. State precisely which two atoms that dashed line connects, and explain why those two.

(c)(i) Propose a temperature to which the mixture should be cooled such that CH3OH and H2CO will both be liquids.

(c)(ii) The scientist analyzes the mixture after it is cooled and determines that 8.59 g of CH3OH(l) is present. Calculate the amount of thermal energy, in kJ, that was removed to condense the 8.59 g of CH3OH at its boiling point.