1. Acids and Bases Special kinds of aqueous solutions “Ionization”
“In nature, acids can be found in fruits: citric acid is responsible for the sharp taste of lemons. Vinegar contains acetic acid, and tannic acid from tree bark is used to tan leather. The stronger mineral acids have been prepared since the Middle Ages. One of these, aqua fortis (nitric acid), was used by assayers to separate gold from silver. Car batteries contain sulfuric acid, also strong and corrosive. A base is the opposite of an acid. Bases often feel slippery; bicarbonate of soda and soap are bases, and so is lye, a substance that can burn skin. Bases that dissolve in water are called alkalis. In water, acids produce hydroxide ions. When an acid and a base react together, the hydrogen and hydroxide ions combine and neutralize each other, forming water together and a salt. The strength of acids and bases can be measured on a pH scale.”
Eyewitness Science “Chemistry” , Dr. Ann Newmark, DK Publishing, Inc., 1993, pg 42

2. Properties ACIDS BASES electrolytes electrolytes sour taste
bitter taste
turn litmus red
turn litmus blue
react with metals to form H2 gas
slippery feel
vinegar, milk, soda, apples, citrus fruits
ammonia, lye, antacid, baking soda
ChemASAP

3. Common Acids Sulfuric Acid H2SO4 Nitric Acid HNO3
Phosphoric Acid H3PO4
Hydrochloric Acid HCl
Acetic Acid CH3COOH
Carbonic Acid H2CO3
Battery acid
Used to make fertilizers
and explosives
Food flavoring
Stomach acid
Vinegar
Carbonated water

4. Common Bases Name Formula Common Name
Sodium hydroxide NaOH lye or caustic soda
Potassium hydroxide KOH caustic potash
Magnesium hydroxide Mg(OH)2 milk of magnesia
Calcium hydroxide Ca(OH) 2 slaked lime
Ammonia water NH3 H2O household ammonia .
NH4OH
NH OH1-
ammonium hydroxide

5. HCl + H2O  H3O+ + Cl– – Definitions +
Arrhenius - In aqueous solution…
Acids form hydronium ions (H3O+)
HCl + H2O  H3O+ + Cl– H Cl O – +
acid
Courtesy Christy Johannesson

6. NH3 + H2O  NH4+ + OH- – Definitions +
Arrhenius - In aqueous solution…
Bases form hydroxide ions (OH-)
NH3 + H2O  NH4+ + OH- H N O – +
base
Courtesy Christy Johannesson

7. Definitions: Brønsted-Lowry
Acid = any substance that donates a proton.
Base = any substance that accepts a proton. 1+ 1- d+ d- +
H2O
H3O+
Cl-
HCl
(acid)
(base)
hydronium ion
chloride ion

8. Definitions: Brønsted-Lowry1+ +
ammonium ion
NH4+ 1-
hydroxide ion
OH- d- d+
NH3
H2O
(base)
(acid)

9. Conjugate Acid-Base Pairs
conjugates
base
acid
HCl H2O H3O Cl-
acid
base
conjugates
HCl H2O H3O Cl-
acid base CA CB

10. Conjugate Acid-Base Pairs
conjugates
acid
base
NH H2O NH OH-
base
acid
conjugates
base acid CA CB
NH H2O NH OH-

11. Acid Strength
Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 508

12. Strength (measured [H+] and [OH-])
Strong Acids/Bases
100% ionized in water
strong electrolytes - +
HCl
HNO3
H2SO4
HBr HI
HClO3
HClO4
Group 1 Hydroxides
(plus Sr(OH)2, Ba(OH)2, and Ca(OH)2)
Courtesy Christy Johannesson

13. Strength (measured [H+] and [OH-])
Weak Acids/Bases
do not ionize completely
weak electrolytes - +
Examples: HF
CH3COOH
H3PO4
H2CO3
HCN
Example:
NH3
Courtesy Christy Johannesson

14. ` pH scale : measures acid/basic concentration 10x 100x 10x 10x
Soren Sorensen
( )
ACID
BASE
10x
100x
10x
10x
NEUTRAL
Each step on pH scale represents a factor of 10.
pH 6 to pH (10X more acidic)
pH 3 to pH (100X less acidic)
pH 8 to pH (100,000X less acidic)

15. pH Scale 7 Acid Base 14 Acidic Neutral Basic [H+] pH 10-14 14 10-13 13
1 M NaOH
Ammonia
(household
cleaner)
Blood
Pure water
Milk
Vinegar
Lemon juice
Stomach acid
1 M HCl
Acidic Neutral Basic
Acid
Base 7 14
pH Scale
“S.P.L. Sorensen ( ) introduced the pH scale to measure the concentration of hydrogen ions in solution. The more hydrogen ions, the stronger the acid. The amount of hydrogen ions in solution can affect the color of certain dyes found in nature. These dyes can be used as indicators to test for acids and alkalis. An indicator such as litmus (obtained from lichen) is red in acid. If base is slowly added, the litmus will turn blue when the acid has been neutralized, at about 6-7 on the pH scale. Other indicators will change color at different pH’s. A combination of indicators is used to make a universal indicator.”
- Eyewitness Science “Chemistry” , Dr. Ann Newmark, DK Publishing, Inc., 1993, pg 42
Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 515

16. pH of Common Substance 14 1 x 10-14 1 x 10-0 0 13 1 x 10-13 1 x 10-1 1
pH [H1+] [OH1-] pOH
14 1 x x
13 1 x x
12 1 x x
11 1 x x
10 1 x x
9 1 x x
8 1 x x
6 1 x x
5 1 x x
4 1 x x
3 1 x x
2 1 x x
1 1 x x
0 1 x x
NaOH, 0.1 M
Household bleach
Household ammonia
Lime water
Milk of magnesia
Borax
Baking soda
Egg white, seawater
Human blood, tears
Milk
Saliva
Rain
Black coffee
Banana
Tomatoes
Wine
Cola, vinegar
Lemon juice
Gastric juice
More basic
7 1 x x
More acidic

17. [H+] [OH-] = 1 x 10-14 M (ionization constant of water (Kw)) pH = - log [H+] pOH = - log [OH-]
Given:
pH = 4.6
Determine [H+]
pH = - log [H+]
choose proper equation
4.6 = - log [H+]
substitute pH value in equation
= log [H+]
multiply both sides by -1
2nd
log
= log [H+]
take antilog of both sides
[H+] = 2.51x10-5 M
10x
antilog
Recall, [H+] = [H3O+]
You can check your answer by working backwards.
pH = - log [H+]
pH = - log [2.51x10-5 M]
pH = 4.6

18. Litmus Paper

19. Indicators phenolphthalein colorless pink acid base weak strong
bromthymol blue
yellow blue
acid base
strong
universal indicator
R O Y G B I V pH

20. pH Paper pH pH

21. Acid-Base Neutralization1+ 1- + +
H3O+
OH-
H2O
H2O
Hydronium ion
Hydroxide ion
Water
Water
Dorin, Demmin, Gabel, Chemistry The Study of Matter 3rd Edition, page 584

22. ACID + BASE  SALT + WATER
Neutralization
ACID + BASE  SALT + WATER
HCl + NaOH  NaCl + H2O
strong
strong
neutral
HC2H3O2 + NaOH  NaC2H3O2 + H2O
weak
strong
basic
Salts can be neutral, acidic, or basic.
Neutralization does not mean pH = 7.
Courtesy Christy Johannesson

23. moles H3O+ = moles OH- MV n = MV n 100% Neutralization M: Molarity
V: volume
n: # of H+ ions in the acid or OH- ions in the base
Courtesy Christy Johannesson

24. Titration Equivalence point (endpoint)
Point at which equal amounts of H3O+ and OH- are present.
Determined by…
indicator color change
dramatic change in pH
Courtesy Christy Johannesson

25. Titration
42.5 mL of 1.3M KOH are required to neutralize 50.0 mL of H2SO4. Find the molarity of H2SO4.
H3O+
M = ?
V = 50.0 mL
n = 2
OH-
M = 1.3M
V = 42.5 mL
n = 1
MVn = MVn
M(50.0mL)(2)
=(1.3M)(42.5mL)(1)
M = 0.55M H2SO4
Courtesy Christy Johannesson

26. Neutralization of Bug Bites
Wasp - stings with base
Red Ant - bites with acid
(neutralize with lemon juice or vinegar)
(neutralize with baking soda)

27. Range and Color Changes of Some Common Acid-Base Indicators
pH Scale 1 2 3 4 5 6 7 8 9 10 11 12 13 14
Indicators
Methyl orange red – yellow
Methyl red red yellow
Bromthymol blue yellow blue
Neutral red red yellow
From F. Brescia et al., Chemistry: A Modern Introduction, W. B. Saunders Co., 1978.
Adapted from R. Bates, Determination of pH, Theory and Practice, John Wiley & Sons, Inc., New York, 1964.
Phenolphthalein colorless red colorless beyond 13.0
Bromthymol blue indicator would be used in titrating a strong acid with a strong base.
Phenolpthalein indicator would be used in titrating a weak acid with a strong base.
Methyl orange indicator would be used in titrating a strong acid with a weak base.