1. Acids and Bases Unit VII

2. I. Electrolytes: a) Definition: substances that when dissolved in water, form a solution capable of conducting electricity. The ability of a solution to conduct electricity is based upon the presence of ions. Examples of electrolytes includes salts (ionic compounds) and certain other polar covalent molecules such as acids and bases.

3. II. Operational and Functional Definitions of Acids and Bases a) The operational definition of a chemical is derived from its observable characteristics. AcidBase Conduct electricity in aqueous solutions React with bases to form salt and water React with acids to form salt and water Cause color changes in acids/base indicators React with certain metals to produce H 2 (g) Taste sour Feel slippery or soapy Operational Definition: Acids and Bases Neutralization

4. HCl + NaOH → NaCl + HOH acid base salt water H 2 SO 4 + 2 NH 4 OH → (NH 4 ) 2 SO 4 + 2 HOH acid base salt water Single Replacement Reaction Zn (s) + HCl (aq) → ZnCl 2(aq) + H 2(g) metal acid salt hydrogen gas

5. **Any metal above H 2 will react with acid to produce hydrogen gas. Which metal below will react with acid to produce H 2 ? Cu or Zn

6. Acid and Base Indicators (Reference Table M) Indicator pH range Color change Methyl orange 3.2 – 4.4 Red to yellow Bromthymol blue 6.0 – 7.6 Yellow to blue Phenolpthalein 8.2 – 10.0 Colorless to pink Litmus 5.5 – 8.2 Red to blue Bromcresol green 3.8 – 5.4 Yellow to blue Thymol blue 8.0 – 9.6 Yellow to blue

7. Bases Effect Indicators Red litmus paper turns blue in contact with a base. Phenolphthalein turns pink in a base.

8. Using Table M What color is Litmus paper in NaOH ? Blue What color is Litmus paper in HCl ? Red What color is Bromthymol blue in a solution with a pH = 5? Yellow What color is Phenolphthalein in a solution with a pH = 11 Pink

9. - There are two conceptual definitions of acids and bases: - There are two conceptual definitions of acids and bases: the Arrhenius and the Bronstead-Lowry Theories the Arrhenius and the Bronstead-Lowry Theories 1.Arrhenius Acids/Bases - Arrhenius acids produce: H 3 O + ions (hydronium) or H + (Hydrogen Ions) in water. HCl (s) + H 2 O (l) H 3 O + (aq) + Cl - (aq) *An acid is a *An acid is a compound with an H first in its formula. Ex: HI, H 2 SO 4, HNO 3 * See Reference Table K for the names and formulas of some common acids. b) The conceptual definition of acids and bases involves using inferences and interpretations of observed properties.

10. Arrhenius Bases produce OH - ions (hydroxide) in water water NaOH(s) Na+(aq) + OH- (aq) Which of the following is a base ? CH3OH or KOH Why isn’t CH3OH a base? It is a non-electrolyte (It has a Carbon) – (it is an alcohol) *Remember all compounds with Carbon (except those that end in COOH) are non-electrolytes. * See Reference Table L for the name and formula of some common bases.

11. Arrhenius Salts Salt - a compound with a metal bonded to a non-metal or negatively charged polyatomic except OH- Examples: NaCl, KNO3, CaCl2

12. Identify The Following As An Acid Base, Salt or Something Else HNO 3HNO 3 KOHKOH MgOMgO CH 3 OHCH 3 OH H 2 SO 4H 2 SO 4 C 2 H 5 OHC 2 H 5 OH CuClCuCl

13. Answers HNO 3HNO 3 -Acid KOHKOH-Base MgOMgO -Salt CH 3 OHCH 3 OH -Something Else H 2 SO 4H 2 SO 4 -Acid C 2 H 5 OHC 2 H 5 OH -Something Else CuClCuCl-Salt

14. Summary of Arrhenius Acid-Base Theory When a base is placed in water, what is the only negative ion present? Hydroxide (OH-) When an acid is placed in water, what is the only positive ion present? Hydronium(H3O+) or Hydrogen (H+) Which compound produces H3O+ as its only positive ion in water? KOH HCl NaCl Which compound produces OH- as its only negative ion in water? KOH HCl NaCl

15. 2.Bronsted –Lowry Acids/Bases - A Bronstead-Lowry Acid is a proton donor (H + ). - A Bronstead-Lowry Base is a proton acceptor (H + ). H 2 O + HCl  H 3 O + + Cl - Proton acceptor Proton donor Therefore H 2 O is a base and HCl is an acid in this theory

16. How Do You Identify A Substance In An Equation As An Acid or Base Using This Theory ? Step 1: In the equation locate the conjugate pairs ( formulas that differ by an H+) Step 2:The one with most H’s is an acid and its pair is a base; together they are called a conjugate acid-base pair Identify the acids and bases in the following: HNO3 + NH3  NH4+ + NO3- Conjugate pairs HNO 3 = acid & NO 3 - = base; NH 4 + = acid & NH3=base

17. Identify The Acids And Bases In The Reactions Below. NH3 + H2O  H3O+ + NH2- a a a acid base acid base H2O + NH2-  NH3 + OH- Acid base acid base HSO4- + Cl-  HCl + SO4-2 acid base acid base

18. Finding Conjugate Acids And Bases of a Formula To find the conjugate acid of a formula add on a H+ (Add Aacid) To find the conjugate base of a formula subtract an H+ (Subtract Base) What is the conjugate acid of each? (Add Aacid) H2O NH3 HSO4- The answers H2O = H3O+ NH3 = NH4+ HSO4- = H2SO4

19. Finding The Conjugate Base Of A Compound To find the conjugate base of a formula subtract an H + (S ubtract B ase )To find the conjugate base of a formula subtract an H + (S ubtract B ase ) What is the conjugate base of eachWhat is the conjugate base of each H 2 OH 2 O NH 4 +NH 4 + HSO 4 -HSO 4 - The answers are:The answers are: H 2 O = OH -H 2 O = OH - NH 4 + = NH 3NH 4 + = NH 3 HSO 4 - = SO 4 -2HSO 4 - = SO 4 -2

20. Identify The Acids and Bases In The Following HCl + H 2 O H 3 O + Cl - NH 3 + H 2 O NH 4 + + OH - Do you see anything unusual above ? Water is an acid in one equation and a base in the other This called an amphiprotic or amphoteric substance acidbaseacidbase acid base

21. Using this table is HCO3 - amphiprotic? yes Is Cl - amphiprotic? no

22. Strong Acids vs. Weak Acids Strong acids are assumed to be 100% ionized in solution (good proton donors). Weak acids are usually less than 5% ionized in solution (poor proton donors). HClH 2 SO 4 HNO 3 H 3 PO 4 HC 2 H 3 O 2 Organic acids

23. Strong Acid Dissociation

24. Weak Acid Dissociation

25. Organic Acids Organic acids all contain the “carboxyl” group, sometimes several of them. *The carboxyl group is a poor proton donor, so ALL organic acids are weak acids.

26. Self - Ionization of Water Self - Ionization of Water Occasionally in water, a H + is transferred between H 2 O molecules Formula: H 2 O + H 2 O  H 3 O + + OH - water molecules hydronium hydroxide ion (+) ion (-)

27. Pure Water is Neutral Pure water contains small, but equal amounts of ions: H 3 O + and OH - H 2 O + H 2 O H 3 O + + OH - hydronium hydroxide ion ion 1 x 10 -7 M 1 x 10 -7 M 1 x 10 -7 M 1 x 10 -7 M H3O+H3O+ OH -

28. Ion Product of Water K w [ ] = Molar concentration K w = [ H 3 O + ] [ OH - ] = [ 1 x 10 -7 ][ 1 x 10 -7 ] = 1 x 10 -14

29. Acids Acids have an increase of H + Acids have an increase of H + HCl (g) + H 2 O (l) H 3 O + (aq) + Cl - (aq) HCl (g) + H 2 O (l) H 3 O + (aq) + Cl - (aq) More [H 3 O + ] than H 2 O, so > 1 x 10 -7 M More [H 3 O + ] than H 2 O, so > 1 x 10 -7 M As H 3 O + increases, OH - decreases As H 3 O + increases, OH - decreases [H 3 O + ] > [OH - ] H3O+H3O+ OH -

30. Bases Increase the hydroxide ions (OH - ) Increase the hydroxide ions (OH - ) H 2 O H 2 O NaOH (s) Na + (aq) + OH - (aq) NaOH (s) Na + (aq) + OH - (aq) More [OH - ] than water, so [OH - ] > 1 x 10 -7 M More [OH - ] than water, so [OH - ] > 1 x 10 -7 M When OH - increases, H 3 O + decreases When OH - increases, H 3 O + decreases [OH  ] > [H 3 O + ] H3O+H3O+ OH -

31. Using K w The [OH - ] of a solution is 1.0 x 10 - 3 M. What is the [H 3 O + ]? K w = [H 3 O + ] [OH - ]= 1.0 x 10 -14 [H 3 O + ] =1.0 x 10 -14 [OH - ] [OH - ] [H 3 O + ] = 1.0 x 10 -14 = 1 x 10 -11 [H 3 O + ] = 1.0 x 10 -14 = 1 x 10 -11 1x 10 -3 1x 10 -3

32. Example Problems 1. The [H 3 O + ] of lemon juice is 1.0 x 10 -3 M. What is the [OH - ] of the solution? 1) 1.0 x 10 3 M 2) 1.0 x 10 -11 M 3) 1.0 x 10 11 M

33. Solution 1. The [H 3 O + ] of lemon juice is 1.0 x 10 - 3 M. What is the [OH - ]? [OH - ] = 1.0 x 10 -14 = 1.0 x 10 -11 1.0 x 10 - 3

34. Using Kw(1 x10 -14 ) 2. What is the [OH - ] when [H 3 O + ] of 1 x 10 - 4 M 1) 1 x 10 -6 M 2) 1 x 10 -8 M 3) 1 x 10 -10 M

35. pH Range 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Neutral Neutral [H + ] > [OH - ] [H + ] = [OH - ] [OH - ] > [H + ] [H + ] > [OH - ] [H + ] = [OH - ] [OH - ] > [H + ] Acidic Basic

36. pH of Some Common Acids gastric juice1.0 lemon juice2.3 vinegar2.8 orange juice3.5 coffee5.0 milk6.6

37. pH of Some Common Bases blood 7.4 tears 7.4 seawater 8.4 milk of magnesia10.6 household ammonia 11.0

38. Finding the pH Finding the pH The pH indicates the acidity [H 3 O + ] of the solution The pH indicates the acidity [H 3 O + ] of the solution pH = - log [H 3 O + ] pH = - log [H 3 O + ] From the French pouvoir hydrogene From the French pouvoir hydrogene (“hydrogen power” or power of (“hydrogen power” or power of hydrogen) hydrogen)

39. In the expression for [H 3 O + ]: 1 x 10 -exponent the exponent = pH the exponent = pH Ex: [H 3 O + ] = 1 x 10 -pH M Quick method of getting pH Quick method of getting pH

40. Finding pH given the [H 3 O + ] 1. If [H 3 O + ] is 1 x 10 -5 M: pH = 5 pH = 5 2. If [H 3 O + ] is 1 x 10 -9 M pH = 9

41. Finding the pH if you know the [OH-] If the [OH-] = 1 x 10 -9, what is the pH ?If the [OH-] = 1 x 10 -9, what is the pH ? **Since you need to get pH you must first find [H 3 O + ] using Kw 1x 10 -14 Solution: 1 x 10 -5 = [H 3 O + ] so pH = 5

42. Finding The pH Of A Strong Acid or Base Given The Molarity Strong Acid Strong Acid 1. What is the pH of 0.0001 M HCl ?1. What is the pH of 0.0001 M HCl ? Step 1: Find the [H 3 O + ] by changing the Molarity of HCl to Scientific Notation Step 1: Find the [H 3 O + ] by changing the Molarity of HCl to Scientific Notation [1 x 10 -4 ] = [H3O+] Step 2 : Get the pH directly Answer 4 2. What is the pH of 0.01 M HI2. What is the pH of 0.01 M HI 2

43. Finding The pH Of A Strong Base 1) Find the pH of 0.001 M KOH1) Find the pH of 0.001 M KOH Step 1: Since you have a base the M given is the [OH] = 1X10 -3 Step 2: Using the K w =1X10 -14 sum rule find the [H+] Step 3 : Get the pH using the [H+] pH=11 2) What is the pH of 0.01 M NaOH? 12 [H+] = 1 x 10 -11

44. Finding [ H 3 O + ] and [OH - ] Given The pH [ H 3 O + ] = 1 x 10 -pH[ H 3 O + ] = 1 x 10 -pH [OH - ] = 1 x 10 -14 (Kw)[OH - ] = 1 x 10 -14 (Kw) 1 x 10 -pH 1 x 10 -pH

45. Example #1 The pH of a soap is 10. What is the [H 3 O + ] of the soap solution? 1) 1 x 10 - 4 M 2) 1 x 10 10 M 3) 1 x 10 - 10 M

46. Example #2 If the pH of a substance is 6, what is the [OH] ?If the pH of a substance is 6, what is the [OH] ?Solution: [H 3 O + ] = 1 x 10 -6[H 3 O + ] = 1 x 10 -6 [ OH-] = 1 x10 -14[ OH-] = 1 x10 -14 1 x 10 -6 1 x 10 -6 [ OH-] = 1 x10 -8

47. Learning Check pH7 Identify each solution as 1. acidic 2. basic3. neutral A. _____ HCl with a pH = 1.5 B. _____ Pancreatic fluid [H + ] = 1 x 10 -8 M C. _____ Sprite soft drink pH = 3.0 D. _____ pH = 7.0 E. _____ [OH - ] = 1 x 10 -10 M F. _____ [H + ] = 1 x 10 -12

48. Example # 3 Identify each solution as 1. acidic 2. basic3. neutral A. _1__ HCl with a pH = 1.5 B. _2__ Pancreatic fluid [H + ] = 1 x 10 -8 M C. _1__ Sprite soft drink pH = 3.0 D. _3__ pH = 7.0 E. _1__ [OH - ] = 1 x 10 -10 M F. _2__ [H + ] = 1 x 10 -12

49. Answer the following A. The [H 3 O + ] of tomato juice is 1 x 10 -4 M. What is the pH of the solution? What is the pH of the solution? 1) - 42)43)8 B. The [OH - ] of an ammonia solution is 1 x 10 -3 M. What is the pH of the solution? (Remember you must know the [ H+] to get pH so use Kw to get it 1 x 10 -3 M. What is the pH of the solution? (Remember you must know the [ H+] to get pH so use Kw to get it 1) 32)113)-11

50. Acids Have a pH less than 7

51. Bases have a pH greater than 7

52. Finding the pH ? pH – numerical scale from 1-14 based on [H+] pH = - log [ H+] Since in Regents Chemistry [ H+] = 1 x 10n pH = - of the exponent of the [H+] What is the pH: If the [H+] = 1 x 10-11 pH =11 If the [H+] = 1 x 10-3 pH = 3 If the [H+] = 1 x 10-2 pH = 2

53. Acid Strength and pH Looking at the chart below what is the relationship between acid strength and pH ? A Molarity of Acid pH.00001 M HCl.0001 M HCl.001 M HCl.01 M HCl.1 M HCl 5 4 3 2 1 **As the concentration increases the pH goes down by one for each 10 fold increase.

54. Regents Type pH Questions 1.I f the pH of solution is 6 and an acid that is 1000X stronger is mixed with the solution what is the new pH ? 3, why The pH is lowered by 1 for each zero) So when a 1OOOX stronger acid is added the pH drops three) 2.I f the pH of solution is 8 and an acid that is 100X stronger is mixed with the solution what is the new pH ? 6 3. If the pH of a solution is 5 and a base 1000X stronger is added what will the new pH be? 8, Why? Because when a base is added you increase the pH by 1 for each zero

55. Acids Neutralize Bases HCl + NaOH  NaCl + H 2 O Neutralization reactions ALWAYS produce a salt and water.

56. Writing Balanced Neutralization Reactions Write the balanced equation for the neutralization reaction below: H 2 SO 4 + NaOH  Step 1 Predict the products of the double replacement reaction Step 2 Check to see if the charge is balanced, if not criss-cross to get the correct formula of the salt H 2 SO 4 + NaOH  Na +1 SO 4 -2 = Na 2 SO 4 Step 3 Balance the equation H 2 SO 4 + NaOH  Na 2 SO 4 + H 2 SO 4 + NaOH  Na 2 SO 4 + H 2 O NaSO 4 + H 2 O 22

57. Products of Neutralization 1. HCl + NaOH  2. H 2 SO 4 + Ca(OH) 2  3. HNO 3 + KOH  The products of neutralization are always a ______ and _______. NaCl + H 2 O CaSO 4 + 2 H 2 O KNO 3 + H 2 O salt water

58. Bases Neutralize Acids Milk of Magnesia contains magnesium hydroxide, Mg(OH) 2, which neutralizes stomach acid, HCl. 2 HCl + Mg(OH) 2 MgCl 2 + 2 H 2 O

59. Titration Problems Laboratory process used to determine the Molarity of an unknown acid or base solution. It is based on the exact neutralization of an acid with a base. (usually the moles of acid equal the moles of base) Titration formula MaVa = Mb Vb Ma = Molarity of the acid Va = Volume of the acid Mb = Molarity of the base Vb = Volume of the base Moles acid =Moles base

60. Titration Problems 1. If 10 ml of 2M HCl are titrated to the endpoint with 20 ml of NaOH, what is the Molarity of NaOH ? Ma Va = Mb Vb 2M 10ml = Mb 20ml 20 ml20 ml Mb = 1M 2. If 20 ml of 5M HCl are titrated to the endpoint with 5 ml of NaOH, what is the Molarity of NaOH ? 20M 5M 20ml = Mb 5ml 5 ml5 ml Mb = 20 M

61. Another Example Using the picture, calculate the M of HCl. Solution: Ma Va = Mb Vb Ma.90 ml =.10 1.2 ml.90.90 Ma =.1333 Ma =.13 (correct sig figs)

62. Titration Lab Example Using the table above, calculate the Molarity of NaOH if it is titrated against 6M HCl? Ma Va = Mb Vb 6M 10 ml = Mb 12ml (average of trials) Mb = 5M

63. More Difficult Titration Question Special Note: If the # of Hs and OHs in the acid and base are not equal you must solve the titration problems differently Ma Va X # OHs = Mb Vb X # Hs If 20 ml of NaOH is exactly neutralized by 10 ml of 2 M H 2 SO 4, what is the molarity of the NaOH. Ma Va X # OHs = Mb Vb X # Hs 2M 10ml X 1 = 20 Mb X 2 Mb =.5 Mb =.5

64. Example # 2 If 20 ml of 2M HCl is exactly neutralized by 20 ml of Ba(OH) 2, what is the molarity of the base? 4M Why? Ma Va X # OHs = Mb Vb X # Hs 20ml 2M X 2 = Mb X 20ml X 1 20ml X 1 20ml X 1 Mb = 4M

65. How Do You Determine The Type Of Hydrolysis A Substance Undergoes ? Hydrolysis – the reaction of salts with water to produce an acid, base or neutral solution HCl + NaOH  NaCl + HOH HCl is the parent acid of NaCl and NaOH is the parent base When K2CO3 is dissolved in water, what type of hydrolysis will occur ?

66. K2CO3 B A Step 1 BA the salt and determine the type of acid and base the parents are.(Go to tables K and L) Parent Base- strong Parent Acid-weak Which ever parent is stronger determines the type hydrolysis. Answer: Basic

67. Answer the Following What type of hydrolysis will each undergo: CuCl2 Acidic Na2CO3 Basic KNO3 Neutral

68. THOUGHT QUESTION Which salt below will produce a water solution with a pH of 11 and turn litmus blue?Which salt below will produce a water solution with a pH of 11 and turn litmus blue? a. FeCl 2 a. FeCl 2 b. K 2 CO 3 b. K 2 CO 3 c. NaNO 3 c. NaNO 3

69. The first three on the lists are strong all other are weak Strong Acids HCl HNO 3 H 2 SO 4 Strong Bases NaOH KOH Ca(OH) 2