Chemistry 19.5

Salts in Solution 19.5 The chemical processes inside a living cell are very sensitive to pH. Human blood is normally maintained at a pH very close to 7.4. You will learn about chemical processes that ensure that the pH of blood is kept near 7.4.

Salt Hydrolysis When is the solution of a salt acidic or basic? 19.5

19.5 Salt Hydrolysis In general, salts that produce acidic solutions contain positive ions that release protons to water. Salts that produce basic solutions contain negative ions that attract protons from water.

19.5 Salt Hydrolysis In salt hydrolysis, the cations or anions of a dissociated salt remove hydrogen ions from or donate hydrogen ions to water.

19.5 Salt Hydrolysis

19.5 Salt Hydrolysis The titration curve for a weak acid and a strong base is compared with the titration curve for a strong acid and a strong base. INTERPRETING GRAPHS a. Identify What is the pH of the equivalence point of each titration? b. Describe Why is the same amount of base used in each titration? c. Apply Concepts Explain why the equivalence points of the two titrations are different.

19.5 Salt Hydrolysis To determine whether a salt solution is acidic or basic, remember the following rules:

19.5 Salt Hydrolysis Vapors of the strong acid HCl(aq) and the weak base NH3(aq) combine to form the acidic white salt ammonium chloride (NH4Cl). Vapors of the strong acid HCl(aq) and the weak base NH3(aq) combine to form the acidic white salt ammonium chloride (NH4Cl).

19.5 Salt Hydrolysis

19.5 Salt Hydrolysis Universal indicator solution has been added to each of these 0.10M aqueous salt solutions. A few drops of universal indicator solution have been added to each of these 0.10M aqueous salt solutions. The color of the indicator shows the following from left to right. Ammonium chloride (NH4Cl), is acidic (pH about 5.3), sodium chloride (NaCl) is neutral (pH 7), and sodium ethanoate (CH3COONa) is basic (pH about 8.7). CH3COONa pH 5.3 NH4Cl pH 5.3 NaCl pH 7

19.5 Buffers Buffers What are the components of a buffer?

19.5 Buffers A buffer is a solution of a weak acid and one of its salts, or a solution of a weak base and one of its salts. The pH of a buffer remains relatively constant when small amounts of acid or base are added. The buffer capacity is the amount of acid or base that can be added to a buffer solution before a significant change in pH occurs.

Buffer of Ethanoic Acid and Sodium Ethanoate 19.5 Buffers Buffer of Ethanoic Acid and Sodium Ethanoate Adding H+ produces additional ethanoic acid. Adding OH- produces additional ethanoate ions. The pH changes very little. The buffer described here is made of ethanoic acid (CH3COOH) and sodium ethanoate, which is the source of ethanoate ions (CH3COO-). To begin, the concentrations of ethanoic acid and ethanoate ions are equal. When either H+ or OH- is added, the buffer produces additional ethanoic acid or ethanoate ions. In both situations, the ratio of [CH3COOH] to [CH3COO-] and consequently, the pH, changes very little.

19.5 Buffers

Discover the chemistry behind buffer action.  Buffers Animation 26 Discover the chemistry behind buffer action.

19.5 Buffers

Conceptual Problem 19.2

for Conceptual Problem 19.2 Problem Solving 19.39 Solve Problem 39 with the help of an interactive guided tutorial. Conceptual problem 19.2

19.5 Section Quiz. 19.5

19.5 Section Quiz. 1. Which of the following reactions would most likely yield a basic salt solution? strong acid + weak base weak acid + weak base strong acid + strong base weak acid + strong base

19.5 Section Quiz. 2. Choose the correct words for the spaces. A buffer can be a solution of a _________ and its _________. weak acid, salt strong acid, salt weak acid, conjugate base weak base, conjugate acid

19.5 Section Quiz. 3. Which of the following equations represents the reaction when a high pH substance is added to a dihydrogen phosphate ion- hydrogen phosphate ion buffer system? H2PO4¯ + OH¯ HPO42¯ + H2O HPO42¯ + OH¯  PO43¯ + H2O H2PO4¯ + H+  H3PO4 HPO42¯ + H+  H2PO4¯

Create your Concept Map using the computer.

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