Unit 7: Equilibrium
Chemistry · Unit 7 · Paper 3

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 3” 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 37 min 34 points0/17 attempted
1

Effect of volume change

2

Le Châtelier's principle

3

Solubility product Ksp

4

ICE table

5

Reaction quotient Q

6

Common ion effect

7

Equilibrium constant K

8

Magnitude of K

9

Small-x approximation

10

Kc and Kp relationship

11

Effect of a catalyst on equilibrium

12

Effect of temperature on K

Short answer 1. Define or explain: pH effect on solubility

3 pts

Short answer 2. Define or explain: Dynamic equilibrium

3 pts

Short answer 3. Define or explain: Q vs K reasoning on a graph

3 pts

Short answer 4. Define or explain: Adding an inert gas at constant volume

3 pts

Free response

10 pts

Silver chloride is a sparingly soluble salt: AgCl(s) ⇌ Ag⁺(aq) + Cl⁻(aq) Ksp = 1.8 × 10⁻¹⁰ at 25 °C

(a) Write the solubility-product expression for AgCl.

(b) Calculate the molar solubility of AgCl in pure water at 25 °C.

(c) Calculate the mass of AgCl that dissolves in 1.00 L of pure water at 25 °C.

(d) Calculate the molar solubility of AgCl in 0.100 M NaCl at 25 °C.

(e) Explain, in terms of Le Châtelier’s principle, why the solubility calculated in (d) differs from that in (b).

(f) Identify the name given to the effect described in part (e).

(g) A student mixes 50.0 mL of 2.0 × 10⁻⁴ M AgNO₃ with 50.0 mL of 2.0 × 10⁻⁴ M NaCl. Calculate the reaction quotient, Q, immediately after mixing.

(h) Using your answer to (g), predict whether a precipitate forms, and justify your prediction.

(i) The dissolution of AgCl is endothermic. Predict the effect of raising the temperature on the molar solubility of AgCl, and justify your prediction.

(j) Silver chloride dissolves readily in aqueous ammonia, forming the complex ion Ag(NH₃)₂⁺. Explain, in terms of equilibrium, why adding ammonia increases the solubility of AgCl.