Chap18Notes - 1036 Chapter 18 1 of 42 1036 Chapter 18 3 of...

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1036 Chapter 18 1 of 42 Chapter 18 Acid-Base Equilibria What are Acids and Bases? Two classes of compounds: acids and bases 3 Definitions of acids and bases: 1. Arrhenius Definition: Acids: Bases: Examples: HCl(aq) NaOH(aq) 1036 Chapter 18 2 of 42 2. Bronsted-Lowry Definition: A c i d s : B a s e s : Deprotonation: Protonation: In an acid-base reaction, a proton is transferred from acid to base. Acids: Bases: HA(aq) + H 2 O H 3 O + (aq) + A - (aq) B(aq) + H 2 O(aq) BH + (aq) +OH(aq) HCl(aq) + H 2 O( l ) H 3 O + (aq) + Cl - (aq) NH 3 (aq) +H 2 O( l ) NH 4 + (aq) +OH - (aq) Or HCl(aq) H + (aq) + Cl - (aq) 1036 Chapter 18 3 of 42 HCl(aq) + NH 3 (aq) Cl - (aq) + NH 4 + (aq) Conjugate acid: Conjugate base: Example Problem : What is the conjugate acid of H 2 PO 4 - ? What is the conjugate base of HCO 3 - ? Example Problem : Identify the conjugate acid-base pairs in HIO 3 (aq) + HC 2 O 4 - (aq) IO 3 - (aq) + H 2 C 2 O 4 (aq) 1036 Chapter 18 4 of 42 Water - Acid or Base? Note the two acid-base reactions examined above: HCl(aq) + H 2 O( l ) H 3 O + (aq) + Cl - (aq) NH 3 (aq) +H 2 O( l ) NH 4 + (aq) +OH - (aq) Water is amphiprotic (amphoteric) : H 2 O( l ) + H 2 O( l ) H 3 O + (aq) + OH - (aq) Or H 2 O( l ) H + (aq) + OH - (aq) rinted with FinePrint - purchase at www.fineprint.com
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1036 Chapter 18 5 of 42 Equilibrium constant expression: (***Pure liquids like H 2 O are omitted) K = K w = ionization constant for w ater Let x = [H + ] = [OH - ] (1:1 mole ratio for H + :OH - ) K w = [H + ][OH - ] K w = [x][x] x = In pure water, there are 1.0 x 10 -7 M H + ions and 1.0 x 10 -7 M OH - ions. K w = 1.0 x 10 -14 at 25 o C 1036 Chapter 18 6 of 42 Another method of expressing H + and OH - concentration: pH and pOH [H + ] = [OH - ] (Neutral) [H+] > [OH-] (Acidic) [H+] < [OH-] (Basic or alkaline) [H + ] = 1.0 x 10 -7 M [OH - ] = 1.0 x 10 -7 M Ex: [H+] = 1.0 x 10 -3 M Ex. [H+] = 1 x 10 -10 M pH = pH = pH = pOH = pOH = pOH = pH = -log [H + ] pOH = -log [OH - ] pH + pOH = 14 1036 Chapter 18 7 of 42 pOH 13 12 11 10 9 8 7 6 5 4 3 2 1 0 pH 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 1 10 -1 10 -2 10 -3 10 -4 10 -5 10 -6 10 -7 10 -8 10 -9 10 -10 10 -11 10 -12 10 -13 10 -14 [H + ] ←←← →→→ Increasing acidity Increasing basicity pH < 7 pH > 7 Neutral pH = 7 Acidic solution: Basic solution: Acidity increases as Basicity increases as 1036 Chapter 18 8 of 42 [H + ], M pH [OH ], M Example 1x10 -15 15 10 = 1x10 1 1x10 -14 14 1 = 1x10 0 1 M NaOH (14.0) 1x10 -13 13 0.01 = 1x10 -1 Lye (13.0) 1x10 -12 12 0.001 = 1x10 -2 Household Ammonia (11.9) 1x10 -11 11 1x10 -3 Milk of magnesia (10.5) 1x10 -10 10 1x10 -4 Detergent Solution (10) 1x10 -9 9 1x10 -5 1x10 -8 8 1x10 -6 Sea water (7.0-8.3) 1x10 -7 7 1x10 -7 Blood (7.4) 1x10 -6 6 1x10 -8 Milk (6.4) 1x10 -5 5 1x10 -9 Unpolluted Rain water (5.6) 1x10 -4 4 1x10 -10 Beer (4.0-4.5) 1x10 -3 3 1x10 -11 Vinegar (2.4-3.4) 0.001 = 1x10 -2 2 1x10 -12 Lemon Juice (2.2-2.4) 0.01 = 1x10 -1 1 1x10 -13 Stomach Acid (1.0-3.0) 1 = 1x10 0 0 1x10 -14 1 M HCl (0) 10 = 1x10 1 -1 1x10 -15 37.7% HCl (-1.1) More Basic More Acidic Neutral rinted with FinePrint - purchase at www.fineprint.com
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1036 Chapter 18 9 of 42
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This note was uploaded on 03/31/2008 for the course BIOL 3534 taught by Professor Moore during the Spring '08 term at Virginia Tech.

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Chap18Notes - 1036 Chapter 18 1 of 42 1036 Chapter 18 3 of...

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