Copyright©2000 by Houghton Mifflin Company. All rights reserved. 1 Chemistry FIFTH EDITION by Steven S. Zumdahl University of Illinois

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 2 Chemistry FIFTH EDITION Chapter 14 Acids and Bases Schedule Chapter 14 Schedule Chapter 14

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4 Caustic Characteristics Greek: kaustikos  kaiein “to burn” Acids & bases corrode nearly everything

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 5 Models of Acids and Bases Arrhenius Concept: Acids produce ______in solution, Bases produce ________ ion. Brønsted-Lowry: Acids are ______ (H + ) donors, Bases are ____________________. HCl + H 2 O  Cl  + H 3 O + __________

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 6 Svante Arrhenius His theory limited because it only applies to ______ solutions & allows only one kind of base – _________ ions.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 7 GENERAL REACTION (Bronsted-Lowry) HA (aq) + H 2 O (l)  H 3 O + (aq) + A - (aq) _________________

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 8 Figure 14.2 The Reaction of an (HA) with HA H 2 O H 3 O + A -

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 9 Figure 14.1 The Reaction of

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 10 Unshared e - pair forms a Covalent bond with the H + ion.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 11 Conjugate Acid/Base Pairs HA(aq) + H 2 O(l)  H 3 O + (aq) + A  (aq) conj conj conj conj acid 1 base 2 acid 2 base 1 conjugate base: everything that remains of the_______________________________ conjugate acid: formed when the _________ _____________________________________

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 12 Acid-Base Models Definition of Acid Example of Acid Definition of Base Example of Base Svante Arrhenius Brønsted- Lowry G.N. Lewis

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 13 Acid Dissociation Constant (K a ) HA(aq) + H 2 O(l)  H 3 O + (aq) + A  (aq) K a =

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 14 Let’s do # 29 together!! HOMEWORK: WebAssign 14.1 – 14.2 Due 2/08/06

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 15 The Reaction of NH 3 with HCl to_____________________________ Bronsted-Lowry Model Reaction can also take place in the___________ NH 3 HCl NH 4 + Cl -

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 16 GENERAL REACTION HA (aq) + H 2 O (l)  H 3 O + (aq) + A - (aq) _______________ Section 14.2 ACID STRENGTH DEFINED BY THE _________________ ______________OF ITS DISSOCIATION REACTION.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 17 Acid Strength 4 Its equilibrium position lies ______________. (HNO 3 )  Yields a ______ conjugate ________. (NO 3  ) Strong Acid: WEAKER _________ THAN ______________. Low Affinity for ________________.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 18

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 19 Acid Strength (continued) 4 Its equilibrium lies___________. (CH 3 COOH) 4 Dissociates to only a _________ extent.  Yields a ____________(it is relatively strong) conjugate base____________. (CH 3 COO  ) Weak Acid:

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 20 Figure 14.4 Graphic Representation of the Behavior of Acids of Different Strengths in Aqueous Solution

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 21 Figure 14.5 Acid Strength Versus Conjugate Base Strength Weak Acid gives a relatively ____________________. Stronger Base than ____ Strong Acid gives a relatively ____________________ ________base than H 2 O

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 22 Figure 14.6 A Strong Acid (a) and a Weak Acid (b) in Water Completely Only a few Ionized

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 23 Open Textbooks to page 662. See Table 14.1 Good Summary!!

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 24 STRONG ACIDS: Virtually every molecules ionizes! MEMORIZE!!!

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 25 H 2 SO 4 ______ H 2 SO 4 (aq)  H + + HSO 4 - (virtually 100%) HSO 4 -  H + + SO 4 - (________ acid) OXYACIDS: ______ proton is Attached to an_______ atom. Examples:________________________

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 26

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 27 Organic Acids Acids with a _________ atom ___________. Have ________ group:_______________ Usually ___________acids Examples:________________, benzoic acid

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Copyright©2000 by Houghton Mifflin Company. All rights reserved. 29 Open Textbook to page 663. See Table 14.2 Values of K a for Some Common Monorproticc Acids See also Appendix 5 on page A24. _______the K a  _________________________ Smaller the K a  ________________________

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 30 Strong Acids ___________ K a given. K a = ________ since [HA] ≈ 0. (Actually ______________to measure.)

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 31 REMEMBER!!! Strong Acids: Their Conjugate Bases are________________. Weak Acids: Their Conjugate Bases are _______________. Open Textbook to page 663. Read Sample Exercise 14.2.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 32 Water as an Acid and a Base Water is _________(it can behave either as an_________________________________). __________________ of Water H 2 O (l) + H 2 O(l)  H 3 O + + OH  acid 1 base 2 –Experiments show that: –K w = _____________________ at 25°C –K w = ______________________

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 33 Figure 14.7 Two Water Molecules React to Form

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 34 Autoionization can occur in other liquids besides Water. _________________________________

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 35 K w = [H + ] [OH - ] Ion Product constant or Dissociation Constant for water At 25°C, K w =

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 36 Since K w is an equilibrium constant, it varies with_____________________. In aqueous solutions at 25  C, no matter the solution contains [H 3 O + ] x [OH - ] = ____________ M 2

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 37 NEUTRAL: [H+] _____[OH-] ACIDIC: [H+] ______ [OH-] BASIC: [H+] ______ [OH-] THREE POSSIBLE SITUATIONS In all cases, [H 3 O + ] x [OH - ] =

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 38 Let’s do # 33, 35, 36, 37 HOMEWORK: WebAssign 14.1 – 14.2 Due 2/08/06

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 39 Section 14.3 The pH Scale Compact, Convenient Way to represent solution acidity. pH is a___________________________

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 40 The pH Scale pH   pH in _______ usually ranges from ________. K w = 1.00  10  14 = [H + ] [OH  ] pK w = As pH rises, pOH ________ (sum = _______).

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 41 If [H + ] = 1.0 x M, then pH = Significant Figures for Logarithms The ____________________in the logarithms is equal to the number of ________________in the original number.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 42 Example [H + ] = 1.0 x M 2 sig. fig. pH = 2 places after the decimal point

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 43 Figure 14.8 The pH Scale and pH Values of Some Common Substances Note: As pH _____ then [H + ] ______ If pH goes down by __, Then [H + ] goes up by ___!

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 44 Let’s do #41, 43 a &c Other log scales pOH = pK = pH + pOH =

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 45 Read Page 669 Quantitative Description of an Acid-Base Equilibrium -- General Strategies.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 46 Section 14.4 CALCULATING THE pH of STRONG ACID Solutions MEMORIZE!!!

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 47 Steps 1) What are the solution components & their chemistry? Strong Acids  _____________________! 2)What are the __________________________?; i.e., what sol’n components are present in relatively large amounts? i.e., what components are significant & which can be ignored?

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 48 Let’s do an example together!!! Let’s do # 47a, 49 c, 51, 53.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 49 Section 14.5 Solving Weak Acid Equilibrium Problems 4 List major species in solution. 4 Choose species that can produce H + and write reactions. 4 Based on K values, decide on dominant equilibrium. 4 Write equilibrium expression for dominant equilibrium. 4 List initial concentrations in dominant equilibrium. See page 673!!!

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 50 Solving Weak Acid Equilibrium Problems (continued) 4 Define change at equilibrium (as “x”). 4 Write equilibrium concentrations in terms of x. 4 Substitute equilibrium concentrations into equilibrium expression. 4 Solve for x the “easy way.” 4 Verify assumptions using 5% rule. 4 Calculate [H + ] and pH.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 51 Let’s DO Problems # 55, 59, 61 Let’s go through together Sample Exercise 14.8 on page 673.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 52 The pH of a Mixture of Weak Acids See Sample Exercise 14.9 page 675 Let’s Do Problems # 63 & 64

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 53 Percent Dissociation (Ionization)

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 54 Let’s Do Problem 65 Note: For solutions of any weak acid HA, _________________________________; BUT The Percent Dissociation _________ as [HA] 0 _____________________. For a given weak acid, the percent dissociation __________ as the acid becomes more ________.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 55 Figure The Effect of Dilution on the Percent Dissociation and (H+) of a Weak Acid Solution

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 56 Calculating K a from Percent Dissociation of a Weak Acid See Sample Exercise page 680 Let’s Do Problem #69 Homework: WebAssign Section 14.5

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 57 Section 14.6 Bases Arrhenius Base: Bronsted-Lowry Base: Basic Solution: pH______________

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 58 Section 14.6 Bases “Strong” and “weak” are used in the same sense for bases as for acids. strong = ________ dissociation (__________________ supplied to solution) NaOH(s)  Na + (aq) + OH  (aq)

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 59 Strong Bases Group 1A Hydroxides Group 2A Hydroxides

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 60 Strong Bases Group 1A Hydroxides NaOH KOH LiOH  very expensive RbOH  very expensive CsOH  very expensive Group 2A Hydroxides Ca(OH) 2 Ba(OH) 2 Sr(OH) 2

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 61 Calculating the pH of Strong Base Solutions Assume ____________ Dissociation pH dominated by OH - from the dissociation. Let’s do #82, together!!! Important & Interesting Information about Bases on Pages 681 – 682. READ!! & Write Summary!

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 62 A base ________ have to contain _ion. Many are _____________________& They increase the hydroxide ion concentration because of their_______________________. NH 3 (aq) + H 2 O (l)  NH 4 + (aq) + OH - (aq) ___________________

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 63 These bases typically have at least_____________________________ that is capable of forming a ______ with a ____________. Examples given at the bottom of page 683. Bases have a _________________located on a ___________ atom.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 64 Substituted Molecules _______________ General Formula Read Chemical Impact on page 684. Write Summary.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 65 Bases (continued) ______ = very little dissociation (or reaction with water) H 3 CNH 2 (aq) + H 2 O(l) 

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 66 Base Dissociation Constant (K b ) B (aq) + H 2 O(l)  BH + (aq) + OH - (aq) K b = These types of Bases are Weak Bases. K b tend to be __________.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 67 Let’s do # 87, 89a, 93b & 95 together!!! Calculate the pH of solutions of Weak Bases Table of K b found in Table 14.3 on page 685 and Appendix A5.3 on page A25.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 68 Section 14.7 Polyprotic Acids... can furnish _____________________to the solution.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 69 All polyprotic acids dissociate in a _________ ___________ -= i.e., one proton at a time. Each ____ has its own equilibrium ________. For a typical weak polyprotic acid i.e., each _______ of dissociation is successively __________.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 70 As protons are lost from polyprotic acids, a ___________ charge on the acid increases. It becomes ___________to remove a _________ charged proton from a __________ charged species.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 71 Let’s look at Examples on page 688 H 2 CO 3 · H 3 PO 4 See Table 14.4 on page 689 for Stepwise Dissociation Constants for Common Polyprotic Acids.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 72 For a typical Polyprotic acid in water, ONLY the _________dissociation step is Important in determining the pH. Therefore, the pH calculation of a weak __________acid is ________ to a weak ___________________acid. Let’s do Problem # 99. Homework: Do on paper #100

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 73 WHAT ABOUT SULFURIC ACID? Sulfuric acid is unique: (1)It is a ______________________________ H 2 SO 4  H + (aq) + HSO 4 - (aq) K a1 = ______ (2) It is a _________________________________. HSO 4 - (aq)  H + (aq) + SO 4 2- (aq) K a2 =__________

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 74 WHAT ABOUT SULFURIC ACID? For conc. of __________________, only the ________makes an important contribution. For dilute concs. (________),the______ dissociation step makes a contribution. Let’s Do # 101 Read Exer & p691

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 75 Section 14.8 Acid-Base Properties of Salts Salts = Salts can behave as _________________.

Copyright©2000 by Houghton Mifflin Company. All rights reserved Salts that produce neutral solutions. Composed of cations and anions. Example: NaCl. NaNO 3, KCl

Copyright©2000 by Houghton Mifflin Company. All rights reserved Salts that produce basic solutions. Composed of cations with and anions which are the Example: NaCH 3 COO Major species: Na + is neutral CH 3 COO - is conjugate base of weak acid H 2 O is weakly amphoteric

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 78 CH 3 COO 1- + H 2 O  CH 3 COOH + OH 1- CH 3 COO 1- in water produces _______ions  __________ solution

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 79 CH 3 COO 1- + H 2 O  CH 3 COOH + OH 1- K B = CH 3 COOH + H 2 O  CH 3 COO 1- + H 1+ K A =

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 80 K A x K B = [CH 3 COO 1- ] [ H 1+ ] x [CH 3 COOH] [OH 1- ] [CH 3 COOH] [CH 3 COO 1- ] = =

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 81 K a x K b = _________ For any weak acid and its conjugate base:

Copyright©2000 by Houghton Mifflin Company. All rights reserved Salts that produce acidic solutions. Composed of cations which are the ________________________and anions with __________ properties. Example: NH 4 Cl Major species: Cl -, H 2 O, & NH 4 + NH 4 1+ (aq)  NH 3 (aq) + H 1+ (aq)

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 83 Let’s Do Problems # 103, 105, 107, 109a, 111

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 84 Another type of salt gives ______ solutions those with Hydrated________________________________ Dissolve ____________ in water. _________________ is formed. It is a ________________ acid. Al(H 2 O) 6 3+ (aq)  Al(OH)(H 2 O) 5 2+ (aq) + H + (aq)

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 85 A ___________ on the ______ ion (Al 3+ ) polarizes the O—H bonds & makes these water molecules more acidic than the O—H bonds ordinarily are in water. Let’s Do Problem # 113

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 86 Salts with that can affect the pH Too complicated to deal with quantitatively. One can if Acidic, Basic or Neutral Compare K a & K b 1.If K a > K b, then 2.If K a < K b, then 3.If K a = K b, then Let’s Do Problem 115

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 87 Acid-Base Properties of Salts See Table 14.6 on page 700

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 88 Section 14.9 Structure and Acid-Base Properties Two factors for acidity in binary compounds: 4 Bond Polarity 4 Bond Strength Read pages

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 89 Oxyacids H—O—X Acid Strength_______________________ ________________________________.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 90 Figure The Effect of the Number of Attached Oxygens on the O-H Bond in a Series of of Chlorine Oxyacids Electronegative oxygen atoms pull _______ away from the Cl atoms & the O—H bond. ______ Strongest Acid

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 91 Hydrated metal ions Example: Al(H 2 O) 6 3+ Greater the ________ on a metal ion the ______ the acidity of the ___________molecules.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 92 Section Acid Base Properties of Oxides A compound containing the H—O—X group Will produce 1. an acidic sol’n in water if the O—X bond is. Example: H 2 SO 4 ; O—S bonds are strong & covalent. Therefore, O—H bonds break to produce protons.

Copyright©2000 by Houghton Mifflin Company. All rights reserved a basic sol’n in water if the O—X bond Is. Example: Na—O—H O—Na bonds are ionic and therefore Break in water to give Na + & OH -

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 94 Oxides Acidic Oxides (Acid ______________):  O  X bond is strong and covalent. 4 Dissolve in water & form acidic sol’ns. 4 _______________ form acid sol’ns in water. SO 2, NO 2, CrO 3 EXAMPLES: SO 3 + H 2 O (l)  H 2 SO 4 (aq) SO 2 + H 2 O (l)  H 2 SO 3 (aq) CO 2 + H 2 O (l)  H 2 CO 3 (aq)

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 95 Oxides Basic Oxides (___________ Anhydrides):  O  X bond is ionic. 4 Dissolve in water & form basic sol’ns. 4 ___________________form basic sol’ns in water. K 2 O, CaO EXAMPLES CaO (s) + H 2 O (l)  Ca(OH) 2 (aq) K 2 O (s) + H 2 O (l)  2 KOH (aq)

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 96 Homework Let’s Do Problems # 117a, 117b, 118a, 118b, 119a, 119 b, 122.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 97 Section Lewis Acids and Bases Lewis Acid: Lewis Base: Acid Base

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 98 Figure The Al(H 2 O) 6 3+ Ion

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 99 Lewis Acid-Base Model – Most ________model for acid-base behavior. Lewis Model encompasses the Bronsted- Lowry model, but the reverse is not true. __________ can be a species _________.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 100 Let’s Do Problems # 123, 125, 127, 128. Additional Exercises # , 133, , 139, 141a Section Strategy for Solving Acid-Base Problems: A Summary READ!!!!!!!!!!!!!!!!!!! ALSO!! Good “Review” p