Acids and Bases
http://www.unit5.org/chemistry/AcidBase.html
Properties
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
Definitions
 Arrhenius
- In aqueous solution…
• Acids form hydronium ions (H3O+)
HCl + H2O  H3O+ + Cl–
H
H
Cl
O
H
O
H
H
–
+
Cl
H
acid
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Definitions
 Arrhenius
- In aqueous solution…
• Bases form hydroxide ions (OH-)
NH3 + H2O  NH4 +
+
H
H
H
N
H
O
H
–
+
O
N
H
H
OH
H
H
base
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H
Brønsted-Lowry Acids and Bases
Acid = any substance that donates a proton.
Base = any substance that accepts a proton.
d+
1-
1+
d-
+
HCl
H2O
H3O+
Cl-
(acid)
(base)
hydronium ion
chloride ion
Brønsted-Lowry Acids and Bases
d-
1-
1+
d+
+
NH3
H2O
(base)
(acid)
NH4+
ammonium ion
OH-
hydroxide ion
Acid – Base Systems
Type
Acid
Base
Arrhenius
H+ or H3O +
producer
OH - producer
BrønstedLowry
Lewis
Proton (H +)
donor
Proton (H +)
acceptor
Electron-pair
acceptor
Electron-pair
donor
Common Acids
Sulfuric Acid
H2SO4
Battery acid
Nitric Acid
HNO3
Used to make fertilizers
and explosives
Phosphoric Acid
H3PO4
Food flavoring
Hydrochloric Acid
HCl
Stomach acid
Acetic Acid
Carbonic Acid
CH3COOH
H2CO3
Vinegar
Carbonated water
Common Bases
Name
Formula
Common Name
Sodium hydroxide
NaOH
lye or caustic soda
Potassium hydroxide
KOH
lye or caustic potash
Magnesium hydroxide
Mg(OH)2
milk of magnesia
Calcium hydroxide
Ca(OH) 2
slaked lime
Ammonia water
NH
H 2O
NH43.OH
household ammonia
NH41+ + OH1ammonium hydroxide
Strength
• Strong Acid/Base
-
+
– 100% ionized in water
– strong electrolyte
HCl
HNO3
H2SO4
HBr
HI
HClO4
NaOH
KOH
Ca(OH)2
Ba(OH)2
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Strength
 Weak
Acid/Base
• does not ionize completely
• weak electrolyte
HF
CH3COOH
H3PO4
H2CO3
HCN
-
+
NH3
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Strong vs. Weak
Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 508
Acid Dissociation
+
H
1-
HCl
Cl
Acid
Conjugate base
Conjugate pair
Kelter, Carr, Scott, Chemistry A World of Choices 1999, page 280
Conjugate Acid-Base Pairs
conjugates
HCl
+
base
acid
H 2O
H3O+
+
acid
Clbase
conjugates
HCl
acid
+
H 2O
H3O+
base
CA
+
ClCB
Conjugate Acid-Base Pairs
conjugates
acid
NH3
+
H2O
base
base
NH41+
+
OH-
acid
conjugates
NH3
base
+
H2O
acid
NH41+
CA
+ OHCB
Acid-Base Neutralization
1-
1+
+
+
H3O+
OH-
H2O
H2O
Hydronium ion
Hydroxide ion
Water
Water
Dorin, Demmin, Gabel, Chemistry The Study of Matter 3rd Edition, page 584
Neutralization of Bug Bites
Wasp - stings with base
Red Ant - bites with acid
(neutralize with lemon juice or vinegar)
(neutralize with baking soda)
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.
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Neutralization
+
O
moles H3 = moles
MVn = MVn
M: Molarity
V: volume
n: # of H+ ions in the acid
or OH- ions in the base
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OH
pH scale: measures acidity/basicity
Soren Sorensen
(1868 - 1939)
ACID
BASE
10x10x
100x 10x
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
NEUTRAL
Each step on pH scale represents a factor of 10.
pH 5 vs. pH 6
pH 3 vs. pH 5
pH 8 vs. pH 13
(10X more acidic)
(100X different)
(100,000X different)
Basic
7
Acid
14
Neutral
pH Scale
Acidic
0
Base
Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 515
[H+]
pH
10-14
14
10-13
13
10-12
12
10-11
11
10-10
10
10-9
9
10-8
8
10-7
7
10-6
6
10-5
5
10-4
4
10-3
3
10-2
2
10-1
1
100
0
1 M NaOH
Ammonia
(household
cleaner)
Blood
Pure water
Milk
Vinegar
Lemon juice
Stomach acid
1 M HCl
pH = - log [H+]
[H+] + [OH-] = 1 x 10-14 M
Given: pH = 4.6
pH = - log [H+]
choose proper equation
4.6 = - log [H+]
substitute pH value in equation
- 4.6 =
2nd
log
determine the [hydronium ion]
- 4.6 =
log [H+]
log [H+]
[H+] = 2.51x10-5 M
multiply both sides by -1
take antilog of both sides
Recall, [H+] = [H3O+]
10x
antilog
You can check your answer by working backwards.
pH = - log [H+]
pH = - log [2.51x10-5 M]
pH = 4.6
pH of Common Substance
More acidic
More basic
pH
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
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
[H1+]
[OH1-]
1 x 10-14
1 x 10-13
1 x 10-12
1 x 10-11
1 x 10-10
1 x 10-9
1 x 10-8
1 x 10-7
1 x 10-6
1 x 10-5
1 x 10-4
1 x 10-3
1 x 10-2
1 x 10-1
1 x 100
1 x 10-0
1 x 10-1
1 x 10-2
1 x 10-3
1 x 10-4
1 x 10-5
1 x 10-6
1 x 10-7
1 x 10-8
1 x 10-9
1 x 10-10
1 x 10-11
1 x 10-12
1 x 10-13
1 x 10-14
pOH
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
Litmus Paper
pH Paper
pH 0
1
2
3
4
5
6
pH 7
8
9
10
11
12
13
Indicators
colorless
weak acid
phenolphthalein
yellow
strong acid
bromthymol blue
universal indicator
&
blue
strong base
R O Y G B I V
pH 4
litmus paper
pink
strong base
pH paper
7
12
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
Methyl red
Bromthymol blue
Neutral red
Phenolphthalein
3.1 – 4.4
red
red
4.4
yellow
yellow
6.2
6.2
red
colorless
6.8
yellow
7.6
8.0
8.0
blue
yellow
10.0
red
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.
colorless beyond 13.0
Titration
 Equivalence
point (endpoint)
• Point at which equal amounts
of H3O+ and OH- have been
added.
• Determined by…
• indicator color change
• dramatic change in pH
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Titration
+
O
moles H3 = moles
MVn = MVn
M: Molarity
V: volume
n: # of H+ ions in the acid
or OH- ions in the base
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OH
Titration
 42.5
mL of 1.3M KOH are required to
neutralize 50.0 mL of H2SO4. Find the
molarity of H2SO4.
H3O+
OH-
M=?
M = 1.3M
V = 50.0 mL
n=2
V = 42.5 mL
n=1
MV# = MV#
M(50.0mL)(2)
=(1.3M)(42.5mL)(1)
M = 0.55M H2SO4
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