The Foundations of Chemistry

OUTLINE

19-1 The Common Ion Effect and

Buffer Solutions

19-2 Buffering Action

19-3 Preparation of Buffer Solutions

19-4 Acid–Base Indicators

Titration Curves

19-5 Strong Acid/Strong Base

Titration Curves

19-6 Weak Acid/Strong Base

Titration Curves

19-7 Weak Acid/Weak Base Titration

Curves

19-8 Summary of Acid–Base

Calculations

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OBJECTIVES

After you have studied this chapter, you should be able to

• Explain the common ion effect and give illustrations of its operation


• Recognize buffer solutions and describe their chemistry


• Describe how to prepare a buffer solution of a specified pH


• Carry out calculations related to buffer solutions and their action


• Explain what acid–base indicators are and how they function


• Describe what species are present at various stages of titration curves for (a) strong
  acids and strong bases, (b) weak acids and strong bases, and (c) weak acids and weak
  bases


• Carry out calculations based on titration curves for (a) strong acids and strong bases
  and (b) weak acids and strong bases

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n the previous chapter we calculated the acidity or basicity of aqueous solutions of

strong acids, strong bases, weak acids, weak bases, and their salts. In this chapter we

will study (1) solutions that have both weak acids and weak bases present, (2) indi-

cators, and (3) titration curves.

It can be a challenge to recognize the type of solution present. Recognition can be

even more difficult if the solution is formed by a partial or total neutralization reaction.

To help you to recognize the various solutions, a summary table (Table 19-7) is included

in Section 19.8. We encourage you to look at the table often as you progress through this

chapter and as you review this and the previous chapter.

THE COMMON ION EFFECT AND BUFFER SOLUTIONS

In laboratory reactions, in industrial processes, and in the bodies of plants and animals, it

is often necessary to keep the pH nearly constant despite the addition of acids or bases.

19-1

The red anthocyanin pigment in the

common geranium is a naturally

occurring acid–base indicator.