Unit 2: Molecular and Ionic Compound Structure and Properties
Chemistry · Unit 2 · Paper 2

Molecular and Ionic Compound Structure 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 20 terms and is the same for everyone, so a teacher can assign “Unit 2, 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

Why ionic solids are brittle

2

Network covalent solids

3

Molecular geometries

4

Expanded octet

5

Bond polarity vs molecular polarity

6

VSEPR theory

7

Bond energy and length

8

Conductivity of ionic compounds

9

Lattice energy

10

Coulombic reasoning for melting point

11

Alloys

12

Hybridization

Short answer 1. Define or explain: Resonance

3 pts

Short answer 2. Define or explain: Covalent bonding

3 pts

Short answer 3. Define or explain: Formal charge

3 pts

Short answer 4. Define or explain: Metallic bonding

3 pts

Free response

4 pts

Complete Lewis diagrams and some physical properties for compounds X and Y are given. Compound X: a central carbon atom bonded to three CH3 groups and to an —OH group. That is, (CH3)3C—OH. Molar mass 74.1 g/mol, boiling point 82°C. Compound Y: a central SILICON atom bonded to three CH3 groups and to an —OH group. That is, (CH3)3Si—OH. Molar mass 90.2 g/mol, boiling point 98°C. The two structures are otherwise identical; only the central atom differs.

(a) Based on VSEPR theory, predict the geometry around the Si atom in compound Y.

(b) A student claims that compound Y has a higher boiling point than that of compound X because compound Y has stronger London dispersion forces. Do you agree or disagree? Justify your answer.

(c) An equimolar mixture of the two compounds is heated. When the mixture reaches 82°C, which compound will have the higher vapor pressure? Justify your answer.

(d) The mixture is heated to 198°C in a sealed, rigid 12.5 L container, at which point both substances are gases and the total pressure in the container is 2.30 atm. Calculate the number of moles of gas particles in the container.