Full Lab Manual
Introduction & Goals
Chemistry & Background
In Your Write-up
In this two-week experiment you will first explore the behavior of monoprotic and polyprotic acids. In week one, you will investigate the acid-base properties of acetic acid, CH3COOH, and phosphoric acid, H3PO4. By titrating, you will examine the acid and conjugate base species present across the pH scale and the composition of buffers at different pH's. In week 2 of this experiment, you will use your knowledge and skills to identify unknown solutions as acids, bases, or buffers and determine their identity from their pKa, pKb or pH values.
To Learn or Review
Properties of Acids and Bases, pH
Zumdahl, pp. 225-227, 240-245
Strength of Acids and Bases, pKa and pKb
Zumdahl, pp. 227-229
Zumdahl, pp. 276-284
Titration Curves and Polyprotic Acids
Zumdahl, pp. 312-316
Many of the common acids, such as HCl, acetic acid (CH3COOH), and ammonium ion (NH4+), have only one hydrogen which is easily transferred to water to form H3O+. These acids are called monoprotic acids. Many other common acids, such as carbonic acid (H2CO3), phosphoric acid (H3PO4), and citric acid (C6H8O7) are known as polyprotic acids, because they have more than one ionizable proton. While the aqueous chemistry of these acids is more complicated than that of the monoprotic ones, we can understand the acid–base behavior of polyprotic acids, such as H3PO4, by extending the concepts used to understand the behavior of monoprotic acids. We will also use the chemistry of acetic acid and its conjugate base, acetate ion, to explore the behavior of buffer solutions, which resist changes in pH. After exploring the behavior of acetic and phosphoric acids in week 1, you can apply what you have learned to unknown solutions, which may be acids, bases, or buffers in week 2.
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