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General Chemistry Principles, Patterns, and Applications, 2011

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A N S W E R S<br />

1.<br />

2.<br />

3. 43 mL<br />

4.<br />

5.<br />

6.<br />

7.<br />

a. dilute 8.33 mL of 12.0 M HCl to 500.0 mL<br />

b. 72 mL<br />

c. 77.0 mL<br />

8.<br />

9.<br />

10.<br />

11. pH at equivalence point = 8.28<br />

Volume of Base Added (mL) 0 5 10 15 20 25<br />

pH 2.19 2.38 2.70 2.89 3.04 3.15<br />

[1] Oxalate salts are toxic for two reasons. First, oxalate salts of divalent cations such as Ca 2+ are<br />

insoluble at neutral pH but soluble at low pH, as we shall see in Chapter 17 "Solubility <strong>and</strong><br />

Complexation Equilibriums". As a result, calcium oxalate dissolves in the dilute acid of the<br />

stomach, allowing oxalate to be absorbed <strong>and</strong> transported into cells, where it can react with<br />

calcium to form tiny calcium oxalate crystals that damage tissues. Second, oxalate forms stable<br />

complexes with metal ions, which can alter the distribution of metal ions in biological fluids.<br />

16.6 Buffers<br />

L E A R N I N G O B JE C T I V E S<br />

1. To underst<strong>and</strong> how adding a common ion affects the position of an acid–base<br />

equilibrium.<br />

2. To know how to use the Henderson-Hasselbalch equation to calculate the pH of a buffer.<br />

Saylor URL: http://www.saylor.org/books<br />

Saylor.org<br />

1522

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