Lesson Plans

Chemistry: The Central Science 9th Edition ©2003

by Brown, LeMay, and Bursten

Weeks 18–19: Equilibrium

Chapter 15: Chemical Equilibrium

This section introduces the basic concepts of equilibrium that we will need for the rest of the course.

College Board Performance Objectives:

• Understand the meaning of dynamic equilibrium.
• Write the equilibrium expression for any chemical reaction.
• Understand the meaning of the magnitude of the value of K_eq.
• Calculate K_eq when given appropriate data.
• Calculate Q, the reaction quotient, to determine if a reaction is at equilibrium and if not determine its direction.
• Knowing the value of K_eq and initial concentrations, calculate equilibrium concentrations.
• Explain how an equilibrium is shifted by stresses (changes in temperature, pressure, or concentration)—Le Chatelier's Principle.
• Explain how temperature changes the value of K_eq.
• Describe the effect of a catalyst on an equilibrium.

College Board Lab Objectives:

Suggested Labs:

Resources:

• Instructor's Resource Manual, pp. 193–203
• Student's Guide, pp. 311–330
• Test Bank, pp. 539–564
• Instructor's Resource CD, Chapter 15

Pacing Guide:

• Equilibrium and the Equilibrium Constant, K_eq—1 day
• Magnitude of K_eq—1 day
• Heterogeneous equilibria—1 day
• Calculations of K_eq and Applications of K_eq—4 days
• Le Chatelier's Principle—1 day
• Block Scheduling
  Equilibrium and the Equilibrium Constant, K_eq, and the Magnitude of K_eq need to be clearly presented. Calculations of K_eq and Applications of K_eq will require plenty of time to work problems. This is another place where the working of exercises is critical to learning. The concept of Le Chatelier's Principle can be presented, and then exercises that involve it can be worked in one block of time.

Key Words:

Suggested Exercises:
Critical thinking questions and end-of-chapter activities are included in these exercises.

• pp. 604–611, # 1, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27, 29, 31, 33, 35, 37, 39, 41, 43, 45, 47, 49, 51, 54, 57, 60, 63, 66, 72.
• eMedia Exercise: p. 611, # 78, 82.

Troubleshooting Tips/Error Traps:

• A chemical equilibrium is dynamic, only the concentrations are constant.
• Solids and liquids are always excluded from equilibrium expression.
• Although K_eq has units, chemists usually do not express them.
• The change line in the ICE box must always have the same ratio as the coefficients in the balanced chemical equation.
• Temperature is the only factor that changes the value of K_eq.
• Pressure will shift an equilibrium if there are more moles of gas on one side of a reaction than the other. Pressure never changes the value of K_eq.