Chapter 16 notes

Chapter 16 notes - Chapter 16 Objectives (Aqueous Ionic...

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Chapter 16 Objectives (Aqueous Ionic Equilibrium) Spring 2084 1. Buffers are a) solutions which contain components that resist large pH change by reacting with added acids or bases. b) the # of moles of the buffer must exceed the moles of added acid or base. c) a buffer contains a weak acid and its conjugate base or a weak base and its conjugate acid. d) buffer solutions can be made to maintain pH at a specific desired value. Example 1: Which of the following aqueous solutions are buffers? Assume all concentrations are 0.100 M unless otherwise specified. a) HCl; NaCl b) NH 3 ; NH 4 Cl c) HNO 2 ; HNO 3 d) 1000 mL .1 M NH 3 added to 500 mL .1 M HCL e) KOH; KCl f) CH 3 COOH; NH 3 2. To see how buffers work, consider the following: Example 2: What is the pH change when 0.0100 mole KOH is added to a liter of water? a) Suppose we added 0.0100 mol KOH to a liter of an aqueous mixture which is 0.0800 M in NH 3 and 0.1200 M NH 4 Cl. K B for NH 3 is 2.0 × 10 -5 . Example 3: What is the pH of the aqueous mixture before the KOH is added? a) choose an equilibrium NH 3 + H 2 O + 4 NH + OH¯ K B = 2.0 × 10 -5 = ] NH [ ] OH ][ NH [ 3 4 - + or + 4 NH + H 2 O NH 3 + H 3 O + K A = 5.0 × 10 -10 = ] NH [ ] O H ][ NH [ 3 3 3 +
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Chapter 16 Objectives (Aqueous Ionic Equilibrium) Spring 2084 b) Both equilibria are valid and we can use either to calculate pH. c)
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This note was uploaded on 04/07/2008 for the course CHEM 0970 taught by Professor Kogut during the Spring '08 term at Pittsburgh.

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Chapter 16 notes - Chapter 16 Objectives (Aqueous Ionic...

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