1. The Chemistry of Acids and Bases
Chemistry I – Chapter 19
To play the movies and simulations included, view the presentation in Slide Show Mode.

2. Acids
Have a sour taste. Vinegar is a solution of acetic acid. Citrus
fruits contain citric acid.
React with certain metals to produce hydrogen gas
And salt.
React with carbonates and bicarbonates to produce carbon dioxide gas
Bases
Have a bitter taste.
Feel slippery. Many soaps contain bases.

3. Example: Mg + 2HCl  MgCl2 + H2

4. Some Properties of Acids
Produce H+ (as H3O+) ions in water (the hydronium ion is a hydrogen ion attached to a water molecule)
Taste sour
Corrode metals
Electrolytes
React with bases to form a salt and water
pH is less than 7
Turns blue litmus paper to red “Blue to Red A-CID”

5. Acid Nomenclature Review
No Oxygen
w/Oxygen
An easy way to remember which goes with which…
“In the cafeteria, you ATE something ICky”

6. Acid Nomenclature Review
HBr (aq)
H2CO3
H2SO3
 hydrobromic acid
 carbonic acid
 sulfurous acid

7. HI (aq) Hydroiodic Acid HCl (aq) Hydrochloric Acid H2SO4 Sulfuric Acid
Name ‘Em!
HI (aq) Hydroiodic Acid
HCl (aq) Hydrochloric Acid
H2SO4 Sulfuric Acid
HNO3 Nitric Acid
HPO4 Phosphoric Acid
HCO3 Carbonic Acid
HOH Water! (Dihydrogen Monoxide)

8. Some Properties of Bases
Produce OH- ions in water
Taste bitter, chalky
Are electrolytes
Feel soapy, slippery
React with acids to form salts and water
pH greater than 7
Turns red litmus paper to blue “Basic Blue”

9. Some Common Bases NaOH sodium hydroxide lye
KOH potassium hydroxide liquid soap
Ba(OH)2 barium hydroxide stabilizer for plastics
Mg(OH)2 magnesium hydroxide Milk of magnesia
Al(OH)3 aluminum hydroxide Maalox (antacid)

10. Acid/Base definitions
Definition #1: Arrhenius (traditional)
Acids – produce H+ ions (or hydronium ions H3O+)
Bases – produce OH- ions
(problem: some bases don’t have hydroxide ions!)

11. Arrhenius acid is a substance that produces
H+ (H3O+) in water
Arrhenius base is a substance that produces
OH- in water

12. A “proton” is really just a hydrogen atom that has lost it’s electron!
A Brønsted-Lowry acid is a proton donor
A Brønsted-Lowry base is a proton acceptor
A “proton” is really just a hydrogen atom that has lost it’s electron!

13. A Brønsted-Lowry acid is a proton donor
A Brønsted-Lowry base is a proton acceptor
base
acid

14. Conjugate Pairs

15. A Brønsted-Lowry acid is a proton donor
A Brønsted-Lowry base is a proton acceptor
conjugate base
base
acid
conjugate acid

16. Acids & Base Definitions
Definition #3 – Lewis
Lewis acid - a substance that accepts an electron pair
Lewis base - a substance that donates an electron pair

17. Lewis Acid/Base Reaction

18. Neutralization Acid+Base=Salt+Water Ex: HCl + NaOH  NaCl + H2O
Ca(OH)2 + HCl  CaCl2 + H2O

19. Complete Acid/Base Worksheet on page 10 and 11

20. The pH scale is a way of expressing the strength of acids and bases
The pH scale is a way of expressing the strength of acids and bases. Instead of using very small numbers, we just use the NEGATIVE power of 10 on the Molarity of the H+ (or OH-) ion. Under 7 = acid = neutral Over 7 = base

21. pH of Common Substances

22. (Remember that the [ ] means Molarity)
Calculating the pH
pH = - log [H+]
(Remember that the [ ] means Molarity)
Example: If [H+] = 1 X pH = - log 1 X 10-10
pH = - (- 10)
pH = 10
Example: If [H+] = 1.8 X 10-5 pH = - log 1.8 X 10-5
pH = - (- 4.74)
pH = 4.74

23. pH = - log(0.15) = 0.82 pH = - log(3.00X10-7) = 6.52 Try These!
Find the pH of these:
1) A 0.15 M solution of Hydrochloric acid
2) A 3.00 X 10-7 M solution of Nitric acid
pH = - log(0.15) = 0.82
pH = - log(3.00X10-7) = 6.52

24. pH calculations – Solving for H+
If the pH of Coke is 3.12, [H+] = ???
10-pH = [H+]
[H+] = = 7.6 x 10-4 M

25. pH calculations – Solving for H+
A solution has a pH of What is the Molarity of hydrogen ions in the solution?
= [H+]
3.16 X 10-9 M = [H+]

26. pOH Since acids and bases are opposites, pH and pOH are opposites!
pOH does not really exist, but it is useful for changing bases to pH.
pOH looks at the perspective of a base
pOH = - log [OH-]
Since pH and pOH are on opposite ends,
pH + pOH = 14

27. =10 0
=10 0 pH
[H+]
[OH-]
pOH

28. [H+], [OH-] and pH
What is the pH of the M NaOH solution?
[OH-] = M (or 1.0 X 10-3 M)
pOH = - log[OH-] = -log
pOH = 3
pH = 14 – 3 = 11

29. The pH of rainwater collected in a certain region of the northeastern United States on a particular day was What is the H+ ion concentration of the rainwater?
[H+] =
[H+] =1.51X10 -5 M
The OH- ion concentration of a blood sample is 2.5 x 10-7 M. What is the pH of the blood?
pOH = -log [2.5 x 10-7 ]
pOH = 6.6
pOH + pH = 14
pH = 14 – pOH = 7.4

30. [OH-] [H+] pOH pH 1.0 x 10-14 [OH-] 10-pOH 1.0 x 10-14 -Log[OH-] [H+]
-Log[H+]
14 - pH pH

31. Calculating [H+], pH, [OH-], and pOH
Problem 1: A chemist dilutes concentrated hydrochloric acid to make two solutions: (a) 1.0 M and (b) M. Calculate the pH, [H+], pH, pOH, and [OH-] of the two solutions at 25°C.
Solution 1:
pH = -log [H+] = -log(1.0) = 0
10-pH = [H+] = = 1
pOH = 14 - pH = 14 – 0 =14
10-pOH = [OH-] = 10-14

32. Calculating [H+], pH, [OH-], and pOH
Problem 1: A chemist dilutes concentrated hydrochloric acid to make two solutions: (a) 1.0 M and (b) M. Calculate the pH, [H+], pH, pOH, and [OH-] of the two solutions at 25°C.
Solution 2:
pH = -log [H+] = -log(0.0024) = 2.62
10-pH = [H+] = =
pOH = 14 - pH = 14 – 2.62 = 11.4
10-pOH = [OH-] = = 3.98X M

33. Calculating [H+], pH, [OH-], and pOH
Problem 2: What is the [H+], pOH, and [OH-] of a solution with pH = 3.67? Is this an acid, base, or neutral?
10-pH = [H+] = = M
pOH = 14 - pH = 14 – 3.67 = 10.3
10-pOH = [OH-] = = 5.01X M

34. Complete pH problems on page 15

35. pH testing There are several ways to test pH
Blue litmus paper (red = acid)
Red litmus paper (blue = basic)
pH paper (multi-colored)
pH meter (7 is neutral, <7 acid, >7 base)
Universal indicator (multi-colored)
Indicators like phenolphthalein
Natural indicators like red cabbage, radishes

36. Paper testing Paper tests like litmus paper and pH paper
Put a stirring rod into the solution and stir.
Take the stirring rod out, and place a drop of the solution from the end of the stirring rod onto a piece of the paper
Read and record the color change. Note what the color indicates.
You should only use a small portion of the paper. You can use one piece of paper for several tests.

37. pH paper

38. pH meter Tests the voltage of the electrolyte
Converts the voltage to pH

39. pH indicators
Indicators are dyes that can be added that will change color in the presence of an acid or base.
Some indicators only work in a specific range of pH
Once the drops are added, the sample is ruined
Some dyes are natural, like radish skin or red cabbage

40. ACID-BASE REACTIONS Titrations
Setup for titrating an acid with a base

41. Titration 1. Add solution from the buret.
2. Reagent (base) reacts with compound (acid) in solution in the flask.
Indicator shows when exact stoichiometric reaction has occurred. (Acid = Base)
This is called NEUTRALIZATION.

42. If it is a 1:1 Ratio between H+ and OH- in their formulas in a neutralization you can use the dilution equation
Mbase X Vbase = Macid X Vacid
HCl + NaOH  H2O + NaCl
1:1 ratio!

43. If it is not a 1:1 molar ratio between H+ and OH- in their formulas (ignore coefficients for this!), then you must MULTIPLY the molarity of the acid by the # of H+ ions over the # of OH- ions in the acid and base formulas before you solve the dilution equation.
Ex. 2NaOH + H2SO4  Na2SO4 + 2H2O
MULTIPLY the molarityacid by 2/1 or 2.
Mbase X Vbase = 2Macid X Vacid

44. LAB PROBLEM #1: Titration Problem.
Given: HCl + NaOH  H2O + NaCl
35.62 mL of NaOH is neutralized with 25.2 mL of M HCl by titration to an equivalence point. What is the concentration of the NaOH?
1:1 Ratio between acid and base!
Mbase X Vbase = Macid X Vacid
Mbase X 35.62mL = M X 25.2mL
Mbase = M X 25.2mL = M
35.62mL

45. LAB PROBLEM #2: Titration Problem.
Given: 2H3PO4 + 2KOH  3H2O + 2KPO4
35.62 mL of KOH is neutralized with 25.2 mL of M H3PO4 by titration to an equivalence point. What is the concentration of the NaOH?
3:1 RATIO -- MULTIPLY THE MOLARITY OF THE ACID BY 3 BEFORE SOLVING!!
Mbase X Vbase = 3Macidx Vacid
Mbase X 35.62mL = 3(0.0998M) X 25.2mL
Mbase = 3(0.0998M) X 25.2mL = M
35.62mL

46. COMPLETE TITRATION PROBLEMS on page 12

47. Oxidation - reduction Chemistry I – Chapter 20
Oxidation is loss of electrons
Reduction is gain of electrons
Oxidation is always accompanied by reduction
The total number of electrons is kept constant
Oxidizing agents oxidize and are themselves reduced
Reducing agents reduce and are themselves oxidized

48. Oxidation numbers
Oxidation number is the number of electrons gained or lost by the element in making a compound
Metals are typically considered more 'cation-like' and would possess positive oxidation numbers, while nonmetals are considered more 'anion-like' and would possess negative oxidation numbers.

49. Loss of Electrons is Oxidation Gain of Electrons is Reduction
Memory Device
LEO the lion says GER
Loss of Electrons is Oxidation
Gain of Electrons is Reduction

50. Predicting oxidation numbers
Oxidation number of atoms in element is zero in all cases
Oxidation number of element in monatomic ion is equal to the charge
Sum of the oxidation numbers in a compound is zero
Sum of oxidation numbers in polyatomic ion is equal to the charge
F has oxidation number –1
H has oxidation no. +1
Oxygen is usually –2.

51. Position of element in periodic table determines oxidation number
G1A is +1
G2A is +2
G3A is +3 (some rare exceptions)
G5A are –3 in compounds with metals
G6A below O are –2 in binary compounds with metals, H or NH4+.
G7A elements are –1 in binary compounds with metals, H or NH4+ or with a heavier halogen.

52. Identifying reagents
Those elements that tend to give up electrons (metals) are typically categorized as reducing agents and those that tend to accept electrons (nonmetals) are referred to as oxidizing agents.

53. Iron can reduce Cu2+ to Cu
The iron nail reduces the Cu2+ ions and becomes coated with metallic Cu. At the same time, the intensity of the blue color diminishes due to loss of Cu2+ ions from solution.

54. Nuggets of redox processes
Where there is oxidation there is always reduction
Oxidizing agent
Reducing agent
Is itself reduced
Is itself oxidized
Gains electrons
Loses electrons
Causes oxidation
Causes reduction

55. Identify redox by change in oxidation numbers: follow the flow of electrons
Reducing agent increases its oxidation number
Oxidizing agent decreases its oxidation number

56. In reactions with metals, nonmetals are always oxidizers (oxidizing agents that are themselves reduced)
Reactions of elements are always redox
The nonmetal gains electrons, becomes a negative ion
The metal loses electrons, becomes a positive ion

57. Oxidation number method
What goes up must come down…
Sum of the changes in oxidation numbers in any process is zero

58. Assign oxidation numbers
Use the rules of oxidation numbers
Element is zero
Monatomic ion: oxidation number is same as charge
Oxide is -2 +2 -1 +7

59. Identify oxidized and reduced
Mn is reduced from +7 to +2
Net gain of 5 electrons
Br is oxidized from -1 to 0
Net loss of 1 electron +2 -1 +7

60. Complete Oxidation/Reduction Problems on page 13