Unit 7: Equilibrium
Chemistry · Unit 7 · Paper 2

Equilibrium 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 17 terms and is the same for everyone, so a teacher can assign “Unit 7, 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

Le Châtelier's principle

2

Common ion effect

3

Effect of a catalyst on equilibrium

4

Magnitude of K

5

Q vs K reasoning on a graph

6

Solubility product Ksp

7

Effect of temperature on K

8

Small-x approximation

9

Relating K for reversed and scaled reactions

10

ICE table

11

pH effect on solubility

12

Dynamic equilibrium

Short answer 1. Define or explain: Adding an inert gas at constant volume

3 pts

Short answer 2. Define or explain: Effect of volume change

3 pts

Short answer 3. Define or explain: Kc and Kp relationship

3 pts

Short answer 4. Define or explain: Reaction quotient Q

3 pts

Free response

4 pts

Strontium hydroxide dissolves in water according to the following equation: Sr(OH)2(s) ⇌ Sr2+(aq) + 2 OH−(aq) Ksp = [Sr2+][OH−]² A student draws a particulate diagram to represent the ions present in an aqueous solution of Sr(OH)2, with water molecules intentionally omitted. The diagram shows 4 Sr2+ ions and 5 OH− ions. The student then prepares a saturated solution by adding excess Sr(OH)2(s) to distilled water and stirring until no more solid dissolves, and determines that [Sr2+] = 0.043 M in the solution.

(a) Identify the error in the student’s drawing.

(b)(i) Calculate the value of [OH−] in the saturated solution.

(b)(ii) Calculate the value of Ksp for Sr(OH)2.

(c) The student prepares a second saturated solution of Sr(OH)2 in aqueous 0.10 M Sr(NO3)2 instead of in water. Will the value of [OH−] in the second solution be greater than, less than, or equal to the value in the first solution? Justify your answer. (Assume constant temperature.)