Lesson Plans

Chemistry: The Central Science 9th Edition ©2003

by Brown, LeMay, and Bursten

Weeks 20–22: Acid-Base Reactions and Solution Equilibria

Chapter 16: Acid-Base Equilibria
Chapter 17: Additional Aspects of Aqueous Equilibria

This is a very important lesson in the chemistry AP* course. It will take at least three weeks to cover it adequately. Much of the exam will deal with concepts learned in this lesson.

College Board Performance Objectives:

• List general properties that characterize acidic and basic solutions and the ions responsible.
• Understand the Brönsted-Lowry theory and be able to identify conjugate acids and bases.
• Explain the autoionization of water and write the K_W expression.
• Define pH and be able to interconvert between [H⁺], [OH^–], pH, and pOH.
• Understand what is meant by strength of an acid or a base.
• Given the acid concentration, be able to interconvert between K_a and pH. Given the base concentration, be able to interconvert between K_b and pH.
• Calculate the percent ionization from the K_a or the K_b, and vice versa.
• Understand the relationship between the strength of an acid and the strength of its conjugate base; interconvert between K_a and K_b.
• Predict whether the solution of a particular salt will be acidic, basic, or neutral.
• Define an acid and a base in the Lewis sense.
• Calculate the concentration of each species in a solution formed by mixing an acid and a base.
• Describe how a buffer solution works and how one can be made at a particular pH.
• Calculate the change in pH of a buffer upon the addition of a strong acid or a strong base.
• Distinguish between the various titration curves.
• Calculate the pH at any point in an acid-base titration.
• Write a K_sp expression for a salt.
• Interconvert between solubility and K_sp.
• Calculate the effect of a common ion on the solubility of a slightly soluble salt.
• Predict whether a precipitate will form when two solutions are mixed.
• Understand the effect of pH on the solubility equilibrium of an acidic or basic ion.

College Board Lab Objectives:

• Learn the operation of a pH meter and how to use it to calculate the K_a of a weak acid.
• Understand the concept of hydrolysis and the behavior of buffer solutions; observe the use of acid base indicators.
• Become familiar with the equilibrium of sparingly soluble salts and determine the value of K_sp.

Suggested Labs:

• Experiment 22, Determination of the Dissociation Constant of a Weak Acid, p. 237
• Experiment 24, Hydrolysis of Salts and pH of Buffer Solutions, p. 269
• Experiment 25, Determination of the K_sp for a Sparingly Soluble Salt, p.287

Resources:

• Instructor's Resource Manual, pp. 204–230
• Student's Guide, pp. 338–388
• Test Bank, pp. 565–615
• Instructor's Resource CD, Chapters 16–17

Pacing Guide:

• Acid-Base Theories: Arrhenius, Brönsted-Lowry, and Lewis—1 day
• Acid Strength—.5 day
• Autoionization of Water, K_W—.5 day
• pH and pOH—.5 day
• Weak Acids and Weak Bases—2 days
• Calculations involving K_a and K_b—2 days
• Acid-Base Properties of Salt Solutions—1 day
• Common-Ion Effect, Buffers—3 days
• Titration Curves—1 day
• K_sp and Precipitation—2 days
• Block Scheduling
  In first block the different theories should be discussed with the idea of acid strength in terms of each. Don't spend a whole lot of time on the Lewis theory. Autoionization of Water and pH and pOH can be covered quickly, but at least two whole blocks will have to be spent on calculations involving K_a and K_b. Hydrolysis of salts and the common-ion effect will be another big topic using at least one block. Buffer solutions and titrated solutions are the most difficult concepts in General Chemistry and will require at least two whole blocks of time. K_sp and precipitation will require a block and a half. It cannot be stressed enough how important it is for the students to work all of the suggested exercises.

Key Words:

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

• pp. 653–659, # 1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27, 31, 33, 35, 37, 41, 43, 45, 47, 49, 51, 53, 55, 59, 61, 63, 65, 67, 69, 71, 73, 75, 77, 99, 109, 112.
• eMedia Exercise: p. 659, # 117, 121.
• pp. 697–701, # 1, 3, 5, 6, 7, 9, 11, 13, 15, 17, 19, 21, 25, 27, 29, 31, 33, 35, 37, 39, 41, 43, 49, 51, 53, 55, 63, 65, 68, 70, 72, 78, 81, 84, 93.
• eMedia Exercise: p. 681, # 96, 97, 98.

Troubleshooting Tips/Error Traps:

• Acid-Base Equilibria is always a major topic on the exam.
• Common-ion effect and buffers are probably the most difficult concepts in General Chemistry and will always appear on the exam.