26. Acids & Bases

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Session Overview

Modules Aqueous Solutions
Concepts Arrhenius, Brønsted-Lowry, and Lewis models of acids and bases, acid strength, pH
Keywords acid, base, alkali, acid-base reaction, proton, electron, donor, acceptor, neutralization, dissociation, ionization, conjugate acid-base pairs, protonation, deprotonation, amphiprotic
Chemical Substances ammonia (NH3), ammonium (NH4), hydronium (H3O+), hydroxyl (OH-), acetic acid (CH3COOH), sulfur dioxide (SO2)
Applications pickling, wine, coal-fired power plant, acid rain, sulfur dioxide scrubber


Before starting this session, you should be familiar with:

Learning Objectives

After completing this session, you should be able to:

  • Compare the acid-base models of Arrhenius, Brønsted-Lowry, and Lewis, and know the salient features of each.
  • Write the general acid-base reaction.
  • Explain the chemical basis of acid strength and the pH measurement.
  • Describe the behaviors of conjugate acid-base pairs.
  • Explain how dissociation affects ionic compounds.
  • Solve specific acid-base reaction problems.


Book Chapters Topics
[Saylor] 4.6, "Acid-Base Reactions." Definitions of acids and bases; polyprotic acids; strengths of acids and bases; hydronium ion; neutralization reactions; pH scale
[Saylor] 8.7, "Lewis Acids and Bases." Lewis acids and bases
[Saylor] 16.1, "The Autoionization of Water." Acid-base properties of water; ion-product constant; relationship among pH, pOH, and pKw
[Saylor] 16.2, "A Qualitative Description of Acid-Base Equilibria." Conjugate acid-base pairs; equilibrium constants Ka, Kb, pKa and pKb; strong acids and bases; leveling effect; polyprotic acids and bases; solutions of salts
[Saylor] 16.3, "Molecular Structure and Acid-Base Strength." Bond strengths; conjugate bases; inductive effects
[Saylor] 16.4, "Quantitative Aspects of Acid-Base Equilibria." Ka and Kb; percent ionization from Ka and Kb; Keq from Ka and Kb

Lecture Video

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This resource may not render correctly in a screen reader.Lecture Slides (PDF - 2.2MB)

Lecture Summary

This lecture introduces the chemical models and behaviors of acids and bases. Starting from the historical origins ("acid" derives from the Latin acidus, meaning "sour"), Prof. Sadoway discusses the evolving acid-base models of Lavoisier (1776), Arrhenius (1887), Brønsted and Lowry (1923), and Lewis (1923-1938).

The lecture proceeds to cover:

  • The general acid-base reaction
  • Conjugate acid-base pairs
  • The dissociation process of ionic compounds
  • Solving acid-base reaction problems


Problems (PDF)

Solutions (PDF)

Textbook Problems

[saylor] Sections Conceptual Numerical
[Saylor] 4.6, "Acid-Base Reactions." 1, 2 none
[Saylor] 16.2, "A Qualitative Description of Acid-Base Equilibria." 2 2
[Saylor] 16.3, "Molecular Structure and Acid-Base Strength." 3 none
[Saylor] 16.4, "Quantitative Aspects of Acid-Base Equilibria." none 8, 15
[Saylor] 16.5, "Acid-Base Titrations." none 1
[Saylor] 16.6, "Buffers." none 3

For Further Study

Supplemental Readings

Buy at Amazon Djerassi, C., and R. Hoffmann. Oxygen: A Play in Two Acts. New York, NY: Wiley-VCH, 2001. ISBN: 9783527304134. See also the study guide and other publisher resources.

Brandis, Kerry. Acid-Base Physiology. See Chapter 1 of this online tutorial/textbook, which applies acid-base chemistry to physiology.


Antoine Lavoisier

Svante Arrhenius1903 Nobel Prize in Chemistry

Johannes Nicolaus Brønsted

Martin Lowry

Gilbert N. Lewis

Other OCW and OER Content

Content Provider Level Notes
5.111 Principles of Chemical Science MIT OpenCourseWare Undergraduate (first-year)

For an alternative treatment of many topics in this session (e.g. acid-base models, pH, equilibrium, acid strength, reaction problems), see:

Lecture 21: Acid-Base Equilibrium

Lecture 22: Chemical and Biological Buffers

Acid-Base Equilibrium Connexions Undergraduate, general chemistry Includes notes and sample exercises


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