1. Acids and Bases Chapters 15 & 16

2. 15.1-Properties of Acids & Bases Pages 453-462

3. Acids-5 common properties 1. Sour taste 2. Turn litmus paper red 3. React with metals more active than hydrogen to produce H 2 gas  Ba (s) + H 2 SO 4(aq)  BaSO 4(aq) + H 2(g) 4. React with bases to produce salts and water 5. Electrolytes

4. Naming Acids Binary acids-contains only 2 elements  Hydrogen and something else Naming rules: 1. Begins with prefix hydro- 2. Root name of the 2 nd element 3. Ends with suffix –ic  Example: HF Hydrofluoric acid  You name: HCl, HI, H 2 S Hydrochloric acid, hydriodic acid, hydrosulfuric acid

5. Naming Acids Be able to write the formula given the name of a binary acid. Example: hydrobromic acid

6. Naming Acids Oxyacid-compound of hydrogen, oxygen, and a 3 rd element (usually nonmetal)  Usually 1+ hydrogens and a polyatomic anion

7. Naming Acids When naming acids involving a polyatomic ion, if the ending…  Is “ate” the acid is named with an “ic”  Is “ite” the acid is named with an “ous”  Example: H 3 PO 4 -phosphoric acid  Example: H 3 PO 3 -phosphorous acid

8. Naming Acids Be able to write the formula of an oxyacid, given the name Examples:  Nitric acid  Sulfurous acid ( hint: the majority of the time, acids start with an “H”, use the crisscross method and cross charges down from the “H” and the polyatomic ion”)

9. Examples of Strong Acids HClO 4 perchloric acid HIhydroiodic acid HBrhydrobromic acid HClhydrochloric acid HNO 3 nitric acid H 2 SO 4 sulfuric acid (diprotic)

10. Examples of Weak Acids CH 3 COOHacetic acid HFhydrofluoric acid HCNhydrocyanic acid HNO 2 nitrous acid HSO 4 - hydrogen sulfate ion

11. Commonly Used Acids Sulfuric acid  Most commonly produced industrial chemical in world  Used in car batteries Nitric acid  Used in making explosives, rubber, and plastics Phosphoric acid  Along with nitrogen and potassium, phosphorus is an essential element for plants and animal. The majority of phosphoric acid produced in used in fertilizers and animal feed.  Diluted solns used as flavoring agent. Hydrochloric acid  Stomach acid  Used to remove impurities from iron and steel, for general cleaning, and to produce other chemicals. Acetic acid  Used in synthesizing chemicals used in the manufacture of plastics and as a fungicide.  A component of vinegar-white vinegar is 4-8% acetic acid

12. Bases-5 common properties 1. Taste bitter 2. Turn litmus paper blue 3. Feel slippery 4. React with acids to produce salts and water 5. Electrolytes What about pH? Do you know what the pH range is for an acid and base??

13. Naming Bases Most of the bases you will see in this class end with a hydroxide ion Examples: Mg(OH) 2 NaOH They are named the same way as naming an ionic compound

14. Examples of Strong Bases NaOHsodium hydroxide KOHpotassium hydroxide Ba(OH) 2 barium hydroxide

15. Examples of weak bases NH 3 ammonia CH 3 NH 2 methylamine C 5 H 5 Npyridine

16. The pH Scale

17. Why is a compound an acid or base? What property is responsible for a compound being classified as an acid or a base??

18. Theories of Acids and Bases Two different theories that describe what defines an acid and a base:  Arrhenius theory  Bronsted-Lowry

19. Arrhenius Acids & Bases Arrhenius noted that aqueous solutions of both acids and bases conduct electric current. Theorized that both must produce ions in solution. BTW-Arrhenius was a Swedish chemist who lived from 1859-1927.

20. Arrhenius Acids & Bases Arrhenius acid-a chemical compound that increases the concentration of hydrogen ions, H +, in solution. Huh?  Arrhenius acids are covalent compounds that ionize when in solution, increasing the number of hydrogen ions present.  Hydrogen ions don’t actually exist free in solution. Instead, they join water to form a hydronium ion, H 3 O +. HNO 3 + H 2 O  H 3 O + + NO 3 -

21. Strength of acids Strong acids-ionize completely in water  All acid molecules ionize to create hydronium ions and anions. No molecules remain. Strong acids are also strong electrolytes. HCl + H 2 O  H 3 O + + Cl -  Every HCl molecule put into solution will ionize to form hydronium and chloride ions. No HCl molecule will remain.

22. Strong Acids The following acids are the common strong acids:  Sulfuric acid, H 2 SO 4  Perchloric acid, HClO 4  Chloric acid, HClO 3  Hydrochloric acid, HCl  Hydrobromic acid, HBr  Hydroiodic acid, HI  Nitric acid, HNO 3

23. Strength of acids Weak acids-do not ionize completely in water.  Solutions of weak acids contain hydronium ions, anions, and dissolved acid molecules. Weak acids are also weak electrolytes. HCN + H 2 O ↔ H 3 O + + CN -  HCN will ionize, but the reverse reaction is also occurring, creating molecules from ions.

24. Arrhenius Acids & Bases Arrhenius base-a chemical compound that increases the concentration of hydroxide ions, OH -, in solution. Huh?  Arrhenius bases are either covalent compounds that ionize when in solution and remove a proton from water, increasing the number of hydroxide ions present or ionic hydroxides that dissociate. Covalent: NH 3 + H 2 O ↔ NH 4 + + OH - Ionic: NaOH  Na + + OH -

25. Strength of bases Strong bases-dissociate completely in water  All base molecules dissociation to create cations and hydroxide ions. All ionic hydroxides are strong bases Strong bases are also strong electrolytes. KOH  K + + OH -  Every unit of KOH put into solution will dissociate into its component ions.

26. Strength of bases Weak bases-do not ionize completely in water.  Solutions of weak bases contain hydroxide ions, cations, and dissolved base molecules. Covalent bases are weak bases Weak acids are also weak electrolytes.

27. Assignment Name the binary acids HBr & H 2 Se. Write formulas for hydrofluoric acid and hydrotelluric acid. Distinguish between binary acids and oxyacids in terms of their component elements. What determines the strength of an Arrhenius acid? Arrhenius base? Give an example of each.

28. Bronsted-Lowry Acids & Bases Some substances that act as acids and bases are not covered by the Arrhenius definitions because they are not in aqueous solution. Bronsted-Lowry definition depends on the ionizable hydrogen.  A Bronsted-Lowry acid is a molecule or ion that is a proton donor.  A Bronsted-Lowry base is a molecule or ion that is a proton acceptor.

29. Bronsted-Lowry Acid A BL acid is a molecule or ion that is a proton donor, meaning it gives up its ionizable hydrogen to another species in the reaction. HCl + NH 3  Cl - + NH 4 +  In the reaction above, hydrochloric acid acts as a BL acid because it donates a proton to ammonia, NH 3. HCl + H 2 O  Cl - + H 3 O +  Hydrochloric acid also acts as a BL acid in a reaction with water, donating a proton to form the hydronium ion, H 3 O +.

30. Bronsted-Lowry Base A BL base is a molecule or ion that is a proton acceptor, meaning it accepts the ionized hydrogen from an acid. HCl + NH 3  Cl - + NH 4 +  In the reaction above, ammonia acts as a BL base because it accepts a proton from HCl to form ammonium, NH 4 +. HCl + H 2 O  Cl - + H 3 O +  What is acting as the BL base in this reaction?

31. Bronsted-Lowry Acid-Base Reactions In a reaction between a Bronsted-Lowry acid and a Bronsted-Lowry base, protons are transferred from one reactant (the acid) to the other (the base).

32. Bronsted-Lowry Acid-Base Example Label each reactant and product in the reactions below as a proton donor (BL acid) or a proton acceptor (BL base).  H 2 CO 3 + H 2 O ⇌ HCO 3 - + H 3 O +  HF + NH 3  NH 4 + + F -  CH 3 NH 2 + H 2 O ⇌ CH 3 NH 3 + + OH - Consider the following reactions. Identify the Arrhenius acids and bases and Bronsted-Lowry acid and bases in these reaction and explain.  NaOH (s)  Na + (aq) + OH - (aq)  HF (aq) + H 2 O (l)  F - (aq) + H 3 O + (aq)  HCl (aq) + NH 3(aq)  NH 4 + (aq) + Cl - (aq)

33. Conjugate Acid-Base Pairs In a BL acid-base reaction, the acid always donates a proton to the base: HX + Y ⇌ X - + HY + The remaining ion or molecule (X - ) can re- accept that proton in the reverse reaction, acting as a base. This base formed by the reaction of a BL acid is known as the conjugate base of the acid. HF + H 2 O ⇌ F - + H 3 O + For example, F- is the conjugate base of HF.

34. Conjugate Acid-Base Pairs Similarly, a base always accepts a proton from an acid in a BL acid-base reaction. HX + Y ⇌ X - + HY + The remaining ion or molecule (HY + ) can donate that proton in the reverse reaction, acting as an acid. This acid formed by the reaction of a BL base is known as the conjugate acid of the base. HF + H 2 O ⇌ F - + H 3 O + For example, H 3 O + is the conjugate acid of H 2 O.

35. Conjugate Acid-Base Pairs BL acid-base reactions reach a state of equilibrium, where both the forward and reverse reaction occur simultaneously. Therefore, they involve two acid-base pairs, known as conjugate acid-base pairs: HF + H 2 O ⇌ F - + H 3 O + Acid + base ⇌ conjugate base + conjugate acid In every conjugate acid-base pair, the acid has one more proton than its conjugate base.

36. Conjugate Acid-Base Pairs In the following reactions, identify the conjugate acid- base pairs:  HCl + H 2 O  H 3 O + + Cl -  H 2 O + HClO 4  ClO 4 - + H 3 O +  CH 3 COOH + H 2 O  H 3 O + + CH 3 COO - Give the conjugate acid of the following BL bases:  H 2 O  PO 4 3-  OH -  NH 3 Give the conjugate base of the following BL acids:  HCO 3 -  H 2 O  H 2 SO 4

37. Amphoteric Compounds Notice that water can act as either a BL acid or base:  Water acting as a base in reaction with HCl: HCl + H 2 O  H 3 O + + Cl -  Water acting as an acid in reaction with CO 3 2- : CO 3 2- + H 2 O  HCO 3 - + OH - Compounds that can act as either an acid or a base are said to be amphoteric. Whether an amphoteric compound will act as an acid or a base in a reaction depends on the conditions of the reaction.

38. 15.3-Acid-Base Reactions Pages 469-475

39. Neutralization Reaction When acidic and basic compounds react with each other, each neutralizes the other. For example:  Antacids, which are basic, help ease indigestion by reacting with & neutralizing excess stomach acid.  Sodium bicarbonate & tartaric acid are 2 components in baking powder. When put into solution, the two compounds produce CO 2 gas which causes foods such as biscuits to rise.

40. Neutralization reactions in aqueous solutions When a strong acid and a strong base in an aqueous solution undergo a neutralization reaction, 2 products are formed:  A salt-an ionic compound composed of a cation from a base and an anion from an acid, and  water.

41. Example Write an equation to represent the neutralization reaction that occurs when aqueous solutions of hydrochloric acid and sodium hydroxide are mixed.

42. Acid Rain Industries produce gases such as NO 2 and SO 2 which dissolve in atmospheric water to produce acidic solutions that fall to the ground. Can dissolve stone, kill aquatic animals, weakens trees pH of acid rain ~ 5.6

43. Implications of Acid-Base Reactions: Acid Rain Many industrial processes produce gases that dissolve in atmospheric water to produce acidic solutions. For example, sulfur trioxide will react with water to form sulfuric acid: SO 3 + H 2 O  H 2 SO 4 Marble used in buildings is made of calcium carbonate, CaCO 3. Carbonates are insoluble in water, but they will act as a BL base in a reaction, ultimately forming a soluble salt, carbon dioxide, and water: H 2 SO 4 + CaCO 3  H 2 CO 3 + CaSO 4  CO 2 + H 2 O + CaSO 4 This causes the marble in buildings and statues to be eroded by the acidic precipitation. The products are harmless, but the damage can be devastating to buildings. Acid rain also is harmful to plants and animals.

44. Effects of Acid Rain

45. 16.1- Aqueous Solutions & the Concept of pH Pages 481-491

46. So… Acids from hydronium ions in solution H3O+H3O+ Bases form hydroxide ions in solution  OH - However, these substances are not the only source of hydronium and hydroxide ions in solution. So what?? Well, this is the basis for the concept of pH.

47. Self-ionization of water Pure water is a extremely weak electrolyte  must contain ions Self-ionization of water-2 water molecules produce a hydronium and a hydroxide ion by transfer of a proton.

48. Concentration of Ions Note: [substance]=conc. in moles/liter In pure water:  [H 3 O + ]=1.0 X 10 -7 M  [OH - ]=1.0 X 10 -7 M Concentrations are inversely related, & the product of them remains constant in pure water & dilute aqueous solutions.

49. Ionization Constant of Water When [H 3 O + ]=[OH - ], a solution is neutral (as in pure water)  [H 3 O + ]=[OH - ]=1.0 X 10 -7 M When [H 3 O + ]>[OH - ], a solution is acidic When [OH - ]>[H 3 O + ], a solution is basic

50. Calculating [H 3 O + ] & [OH - ] Recall that strong acids & bases dissociate completely in solution.  1 mol of NaOH will dissociate in solution to yield 1 mol of Na + & 1 mol of OH - If [H 3 O + ][OH - ]=1.0 x 10 -14 M 2, then you can solve for the concentration of one ion given the other.

51. Which are strong acids/bases? Strong acids:  HCl, HBr, HI, HClO 4, HNO 3, H 2 SO 4 Strong bases:  Group 1 and group 2 metal hydroxides MOH and M(OH) 2 These will dissociate completely in solution. You can assume that acids and bases that I ask you to work problems for are strong.

52. Calculating [H 3 O + ] & [OH - ] Calculate [H 3 O + ] & [OH - ] for a 1.0 x 10 -2 M NaOH solution. Is this solution acidic or basic? Because [OH - ]>[H 3 O + ], this solution is basic.

53. Calculating [H 3 O + ] & [OH - ] Determine the hydronium & hydroxide ion concentrations in a solution that is 1 X 10 -4 M HCl. Acidic or basic? Because [H 3 O + ]>[OH - ], this solution is acidic.

54. Calculating [H 3 O + ] & [OH - ] Determine the hydronium & hydroxide ion concentrations in a solution that is 1 X 10 -4 M Ca(OH) 2. Acidic or basic? Because [OH - ]>[H 3 O + ], this solution is basic.

55. Examples Determine [H 3 O + ] & [OH - ] for the following:  0.01M solution of HClO 4  0.03M solution of NaOH  1.0 X 10 -3 M solution of HNO 3 An aqueous solution of Ba(OH) 2 has a [H 3 O + ] of 1x10 -11 M. What is the [OH - ]? What is the molarity of the solution?

56. The pH Scale Because [H 3 O + ] & [OH - ] can be very small, pH is commonly used to express the hydronium ion concentration. French words pouvoir hydrogene, meaning “hydrogen power” pH-the negative of the common logarithm of the hydronium ion concentration

57. The pH Scale

58. pH & pOH pH=-log[H 3 O + ] For example, the pH of a neutral solution in which [H 3 O + ]=1 X 10 -7 M is: pH=-log(1 X 10 -7 )=-(-7)=7 pOH can also be calculated & represents the hydroxide ion concentration: pOH=-log[OH - ]

59. pH & pOH Remember that [H 3 O + ] & [OH - ] are related by K w : K w =[H 3 O + ][OH - ]=1.0 X 10 -14 M 2 Therefore: pH + pOH =14.0

60. Example What is the pH of a 1.0 X 10 -3 M NaOH solution?

61. Example What is the pH & pOH of a 2.5 X 10 -6 M HNO 3 solution?

62. Calculating [H 3 O + ] & [OH - ] from pH & pOH pH=-log[H 3 O + ]  [H 3 O + ]=10 -pH pOH=-log[OH - ]  [OH - ]=10 -pOH

63. Example Determine the hydronium ion concentration of an aqueous solution that has a pH of 4.0.

64. Example Determine [H 3 O + ] & [OH - ] for a solution that has a pOH of 8.0.

65. More Examples Determine the pH & pOH of the following:  1 X 10 -3 M HCl  3.5 X 10 -2 M Ca(OH) 2 Determine [H 3 O + ] & [OH - ] for the following:  Solution that has a pH of 5.0.  Solution that has a pOH of 4.7.