1 Chapter Learning Objectives a.The chemical properties of acids and bases. b.Acids and bases react with each other in a reaction known as neutralization. c.Acids are proton (H + ) donors; bases are proton acceptors that produce OH - in solution. d.Learn some common acids and bases and their properties, such as their strengths. e.The pH measures the acidity of a solution: pH 7.0 is basic; pH = 7.0 is neutral. f.Buffers are important for maintaining our health.

2 a. Acids Arrhenius acids produce H + ions in water. H 2 O HCl(g) H + (aq) + Cl - (aq) are electrolytes. have a sour taste. turn litmus red. neutralize bases. Hydronium ion – a hydrated proton, H 3 O + = H +

3 Names of Acids Acids with H and a nonmetal are named with the prefix hydro and end with ic acid. HClhydrochloric acid Acids with H and a polyatomic ion are named by changing the end of the name of the polyatomic ion from ate to ic acid or ite to ous acid. ClO 3 − chlorate HClO 3 chloric acid ClO 2 − chlorite HClO 2 chlorous acid

4 Names of Some Common Acids

5 Select the correct name for each of the following acids. A. HBr 1. bromic acid 2. bromous acid 3. hydrobromic acid B. H 2 CO 3 1. carbonic acid 2. hydrocarbonic acid 3. carbonous acid C. HBrO 2 1. bromic acid 2. hydrobromous acid 3. bromous acid Learning Check

6 A. HBr3. hydrobromic acid The name of an acid with H and one nonmetal uses the prefix hydro and ends with ic acid. B. H 2 CO 3 1. carbonic acid An acid with H and a polyatomic ion is named by changing the end of an ate ion to ic acid. C. HBrO 2 3. bromous acid This acid of bromite (BrO 2 - ) is bromous acid. Solution

7 a. Bases Arrhenius bases produce OH − ions in water. taste bitter or chalky. are electrolytes. feel soapy and slippery. neutralize acids.

8 Some Common Bases Bases with OH - ions are named as the hydroxide of the metal in the formula. NaOHsodium hydroxide KOHpotassium hydroxide Ba(OH) 2 barium hydroxide Al(OH) 3 aluminum hydroxide Fe(OH) 3 iron(III) hydroxide

9 Match the formulas with the names. A. ___HNO 2 1) iodic acid B. ___Ca(OH) 2 2) sulfuric acid C. ___H 2 SO 4 3) sodium hydroxide D. ___HIO 3 4) nitrous acid E. ___NaOH5) calcium hydroxide Learning Check

10 Match the formulas with the names. A. 4 HNO 2 nitrous acid B. 5 Ca(OH) 2 calcium hydroxide C. 2 H 2 SO 4 sulfuric acid D. 1 HIO 3 iodic acid E. 3 NaOHsodium hydroxide Solution

11 Comparing Acids and Bases

12 Identify each as a characteristic of an A) acid or B) base. ____1. has a sour taste ____2. produces OH - in aqueous solutions ____3. has a chalky taste ____4. is an electrolyte ____5. produces H + in aqueous solutions Learning Check

13 Identify each as a characteristic of an A) acid or B) base. A 1. has a sour taste B 2. produces OH - in aqueous solutions B 3. has a chalky taste A, B 4. is an electrolyte A 5. produces H + in aqueous solutions Solution

14 Definitions Acidic Solutions – A solution that contains a higher concentration of H 3 O + ions than OH - ions. Basic Solutions (Alkaline solution) – A solution that contains a higher concentration of OH - ions than H 3 O + ions Salt – Ionic compounds composed of the cation from a base and the anion from an acid. Neutralization Reaction – Reaction of equivalent quantities of an acid and a base

15 In a neutralization reaction an acid such as HCl reacts with a base such as NaOH. HCl + H 2 OH 3 O + + Cl − NaOHNa + + OH − the H 3 O + from the acid and the OH − from the base form water. H 3 O + + OH − 2 H 2 O b. Neutralization Reactions

16 In the equation for neutralization, an acid and a base produce a salt and water. acid base salt water HCl + NaOH NaCl + H 2 O 2HCl + Ca(OH) 2 CaCl 2 + 2H 2 O Neutralization Equations

17 HCl(aq) + KOH(aq)  H 2 O(aq) + KCl(aq) Neutralization of H 2 O H 3 O + (aq) + OH - (aq)  H 2 O(l) + H 2 O(l) H 2 SO 4 (aq) + 2NaOH(aq)  2H 2 O(l) + Na 2 SO 4 (aq) base acid water salt

18 In water, H + is transferred from one H 2 O molecule to another. one water molecule acts as an acid, while another acts as a base. H 2 O + H 2 O H 3 O + + OH − :O: H + H:O: H:O:H + + :O:H − H H H water water hydronium hydroxide ion (+) ion (-) Ionization of Water Run the following web animations/movies. 9.3: The Autoionization of Water

19 Pure Water is Neutral In pure water, the ionization of water molecules produces small, but equal quantities of H 3 O + and OH − ions. molar concentrations are indicated in brackets as [H 3 O + ] and [OH − ]. [H 3 O + ] = 1.0 x 10 − 7 M [OH − ] = 1.0 x 10 − 7 M Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings

20 Acidic Solutions Adding an acid to pure water increases the [H 3 O + ]. cause the [H 3 O + ] to exceed 1.0 x M. decreases the [OH − ].

21 Basic Solutions Adding a base to pure water increases the [OH − ]. causes the [OH − ] to exceed 1.0 x 10 − 7 M. decreases the [H 3 O + ]. Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings

22 Comparison of [H 3 O + ] and [OH − ]

23 The ion product constant, K w, for water is the product of the concentrations of the hydronium and hydroxide ions. K w = [ H 3 O + ] [ OH − ] can be obtained from the concentrations in pure water. K w = [ H 3 O + ] [ OH − ] K w = [1.0 x 10 − 7 M] x [ 1.0 x 10 − 7 M] = 1.0 x 10 − 14 Ion Product of Water, K w

24 [H 3 O + ] and [OH − ] in Solutions In neutral, acidic, or basic solutions, the K w is always 1.0 x 10 −14.

25 Guide to Calculating [H 3 O + ]

26 Calculating [H 3 O + ] What is the [H 3 O + ] of a solution if [OH − ] is 5.0 x M? STEP 1: Write the K w for water. K w = [H 3 O + ][OH − ] = 1.0 x 10 −14 STEP 2: Rearrange the K w expression. [H 3 O + ] = 1.0 x [OH − ] STEP 3: Substitute [OH − ]. [H 3 O + ] = 1.0 x = 2.0 x M 5.0 x

27 If lemon juice has [H 3 O + ] of 2 x 10 −3 M, what is the [OH − ] of the solution? 1) 2 x 10 −11 M 2) 5 x 10 −11 M 3) 5 x 10 −12 M Learning Check

28 3) 5 x 10 −12 M Rearrange the K w to solve for [OH - ] K w = [H 3 O + ][OH − ] = 1.0 x 10 −14 [OH − ] = 1.0 x = 5 x 10 −12 M 2 x Solution

29 The [OH − ] of an ammonia solution is 4.0 x 10 −2 M. What is the [H 3 O + ] of the solution? 1) 2.5 x 10 − 11 M 2) 2.5 x 10 −12 M 3) 2.5 x 10 −13 M Learning Check

30 3) 2.5 x 10 −13 M [ H 3 O + ] = 1.0 x 10 −14 = 2.5 x 10 −13 M 4.0 x 10 −2 Solution

31 c. Br Ø nsted-Lowry Acids and Bases According to the Br Ø nsted-Lowry theory, acids donate a proton (H + ). bases accept a proton (H + ). Run the following web animations/movies. 9.1: Proton Transfer with an Acid & a Base 9.2: Reacting with Water

32 NH 3, a Br Ø nsted-Lowry Base In the reaction of ammonia and water, NH 3 is the base that accept H +. H 2 O is the acid that donates H +.

33 A strong acid completely ionizes (100%) in aqueous solutions. HCl(g) + H 2 O(l) H 3 O + (aq) + Cl − (aq) A weak acid dissociates only slightly in water to form a few ions in aqueous solutions. H 2 CO 3 (aq) + H 2 O(l) H 3 O + (aq) + HCO 3 − (aq) d. Strengths of Acids

34 Strong Acids In water, the dissolved molecules of a strong acid dissociate into ions. give large concentrations of H 3 O + and the anion (A - ). Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings

35 Weak Acids In weak acids, only a few molecules dissociate. most of the weak acid remains as the undissociated (molecular) form of the acid. the concentrations of the H 3 O + and the anion (A - ) are small. Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings HA(aq) + H 2 O(l) H 3 O(aq) + A − (aq)

36 Strong and Weak Acids In an HCl solution, the strong acid HCl dissociates 100%. A solution of the weak acid CH 3 COOH contains mostly molecules and a few ions.

37 Strong acids make up six of all the acids. have weak conjugate bases. Strong Acids

38 Weak Acids Weak acids make up most of the acids. have strong conjugate bases.

39 Comparing Strong and Weak Acids

40 Strong Bases Strong bases are formed from metals of Groups 1A (1) and 2A (2). include LiOH, NaOH, KOH, and Ca(OH) 2. dissociate completely in water. KOH(s) K + (aq) + OH − (aq)

41 Weak Bases Weak bases are most other bases. dissociate only slightly in water. form only a few ions in water. NH 3 (g) + H 2 O(l) NH 4 + (aq) + OH − (aq)

42 Learning Check Identify each of the following as a strong or weak acid or base. A. HBr B. HNO 2 C. NaOH D. H 2 SO 4 E. Cu(OH) 2

43 Solution Identify each of the following as a strong or weak acid or base. A. HBrstrong acid B. HNO 2 weak acid C. NaOHstrong base D. H 2 SO 4 strong acid E. Cu(OH) 2 weak base

44 Learning Check Identify the stronger acid in each pair. 1. HNO 2 or H 2 S 2. HCO 3 − or HBr 3. H 3 PO 4 or H 3 O +

45 Solution Identify the stronger acid in each pair. 1. HNO 2 2. HBr 3. H 3 O +

46 Molarity (M) Molarity (M) is a concentration term for solutions. gives the moles of solute in 1 L solution. moles of solute liter of solution

47 What is the molarity of L NaOH solution if it contains 6.00 g NaOH? STEP 1 Given 6.00 g NaOH in L solution Need molarity (mole/L) STEP 2 Plan g NaOH mole NaOH molarity Calculation of Molarity

48 Calculation of Molarity (cont.) STEP 3 Conversion factors 1 mole NaOH = 40.0 g 1 mole NaOH and 40.0 g NaOH 40.0 g NaOH 1 mole NaOH STEP 4 Calculate molarity g NaOH x 1 mole NaOH = mole 40.0 g NaOH mole = mole = M NaOH L 1 L

49 What is the molarity of 325 mL of a solution containing 46.8 g of NaHCO 3 ? 1) M 2) 1.44 M 3) 1.71 M Learning Check

50 3) 1.71 M 46.8 g NaHCO 3 x 1 mole NaHCO 3 = mole NaHCO g NaHCO mole NaHCO 3 = 1.71 M NaHCO L Solution

51 e. pH Scale The pH of a solution is used to indicate the acidity of a solution. has values that usually range from 0 to 14. is acidic when the values are less than 7. is neutral with a pH of 7. is basic when the values are greater than 7. A pH Meter

52 pH of Everyday Substances Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings

53 Identify each solution as 1) acidic 2) basic3) neutral A. ___ HCl with a pH = 1.5 B. ___ pancreatic fluid [H 3 O + ] = 1 x 10 −8 M C. ___ Sprite ® soft drink pH = 3.0 D. ___ pH = 7.0 E. ___ [OH − ] = 3 x 10 −10 M F. ___ [H 3 O + ] = 5 x 10 −12 Learning Check

54 A. 1 HCl with a pH = 1.5 B. 2 Pancreatic fluid [H 3 O + ] = 1 x 10 −8 M C. 1 Sprite ® soft drink pH = 3.0 D. 3 pH = 7.0 E. 1 [OH - ] = 3 x 10 −10 M F. 2 [H 3 O + ] = 5 x 10 −12 Solution

55 Testing the pH of Solutions The pH of solutions can be determined using a) pH meter b) pH paper c) indicators that have specific colors at different pH values. Run the following web animations/movies. 9.4a: Detecting Acid-Base Rxns Using a pH Meter 9.4b: pH Changes using HCl to Water

56 pH is the negative log of the hydronium ion concentration. pH = - log [H 3 O + ] Example: For a solution with [H 3 O + ] = 1 x 10 −4 pH =−log [1 x 10 −4 ] pH = - [-4.0] pH = 4.0 Note: The number of decimal places in the pH equals the significant figures in the coefficient of [H 3 O + ] SF in 1 x Calculating pH

57 Guide to pH Calculations

58 Significant Figures in pH When expressing log values, the number of decimal places in the pH is equal to the number of significant figures in the coefficient of [H 3 O + ]. [H 3 O + ] = 1 x pH = 4.0 [H 3 O + ] = 8.0 x pH = 5.10 [H 3 O + ] = 2.4 x pH = 7.62

59 Find the pH of a solution with a [H 3 O + ] of 1.0 x 10 −3 : STEP 1 Enter [H 3 O + ] Enter 1 x by pressing 1 (EE) 3 The EE key gives an exponent of 10 and change sign (+/- key or – key) STEP 2 Press log key and change sign - log (1 x 10 −3 ) = -[-3] STEP 3 Adjust figures after decimal point to equal the significant figures in the coefficient Two significant figures in 1.0 x 10 −3 Calculating pH

60 Learning Check What is the pH of coffee if the [H 3 O + ] is 1 x 10 −5 M? 1) pH = 9.0 2) pH = 7.0 3) pH = 5.0

61 Solution What is the pH of coffee if the [H 3 O + ] is 1 x 10 −5 M? 3) pH = 5.0 pH = -log [1 x 10 −5 ] = -(-5.0) = 5.0

62 A. The [H 3 O + ] of tomato juice is 2 x 10 −4 M. What is the pH of the solution? 1) 4.02) 3.73) 10.3 B. The [OH − ] of a solution is 1.0 x 10 −3 M. What is the pH of the solution? 1) 3.002) ) Learning Check

63 A. 2) 3.7 pH = - log [ 2 x ] = (EE) 4 (+/-) log (+/-) B. 2) Use the K w to obtain [H 3 O + ] = 1.0 x 10 − 11 pH = - log [1.0 x 10 − 11 ] 1.0 (EE) 11 (+/-) log (+/-) Solution

64 [H 3 O + ], [OH - ], and pH Values Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings

65 Calculating [H 3 O + ] from pH The [H 3 O + ] can be expressed by using the pH as the negative power of 10. [H 3 O + ] = 1 x 10 -pH For pH = 3.0, the [H 3 O + ] = 1 x On a calculator 1. Enter the pH value Change sign Use the inverse log key (or 10 x ) to obtain the [H ]. = 1 x M

66 A. What is the [H 3 O + ] of a solution with a pH of 10.0? 1) 1 x 10 −4 M 2) 1 x M 3) 1 x 10 −10 M B. What is the [OH − ] of a solution with a pH of 2.00? 1) 1.0 x 10 − 2 M 2) 1.0 x 10 −12 M 3) 2.0 M Learning Check

67 A. What is the [H 3 O + ] of a solution with a pH of 10.0? 3) 1 x M1 x 10 -pH B. What is the [OH − ] of a solution with a pH of 2.00? 2) 1.0 x 10 −12 M [H 3 O + ] = 1.0 x 10 −2 M 1 x 10 -pH [OH − ] = 1.0 x 10 −14 = 1.0 x 10 −12 M 1.0 x 10 −2 M Solution

68 f. Buffers When an acid or base is added to water, the pH changes drastically. to a buffer solution, the pH is maintained; pH does not change.

69 Buffers resist changes in pH from the addition of acid or base. in the body, absorb H 3 O + or OH - from foods and cellular processes to maintain pH. are important in the proper functioning of cells. in blood maintain a pH close to 7.4. A change in the pH of the blood affects the uptake of oxygen and therefore cellular processes. Buffers

70 A buffered solution contains a combination of acid-base conjugate pairs. may contain a weak acid and a salt of its conjugate base. typically has equal concentrations of a weak acid and its salt. may also contain a weak base and a salt of the conjugate acid. Components of a Buffer

71 In the acetic acid/acetate buffer with acetic acid (CH 3 COOH) and sodium acetate (CH 3 COONa) The salt produces acetate ions and sodium ions. CH 3 COONa(aq) CH 3 COO - (aq) + Na + (aq) The salt is added to provide a higher concentration of the conjugate base CH 3 COO - than the weak acid alone. CH 3 COOH(aq) + H 2 O(l) CH 3 COO - (aq) + H 3 O + (aq) Large amount Large amount Buffer Action

72 Key Words Acid Base Indicator Hydronium ion (H 3 O + ) Polyprotic acid Strong acid Weak acid Alkali Hydroxide ion (OH - ) pH meter Strong base Weak base Amphoteric pH Neutral solution Conjugate acid-base pair Buffer Neutralization