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Acids and Bases
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Acids, Bases, and Salts
You should be able to
➢Understand the acid-base theories of Arrhenius, Brønsted-Lowry,
and Lewis.
➢Identify strong acids and bases and calculate their pH‟s.
➢Calculate the pH of a weak acid or base.
➢Calculate the concentration of a strong or weak acid or base from
its pH.
➢Calculate the pH and ion concentration in a polyprotic acid.
➢Predict the pH of a salt from its formula and then calculate the pH
of the salt.
➢Be familiar with titration curves and selection of an acid-base
indicator.
pH scale
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
ACID BASE
NEUTRAL
Each step on pH scale represents a factor of 10.
pH 5 vs. pH 6 (10X more acidic) pH 3 vs. pH 5 (100X different)
pH 8 vs. pH 13 (100,000X different)
: measures acidity/basicity
10x 10x 10x 100x
pH scale
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
ACID BASE
NEUTRAL
Each step on pH scale represents a factor of 10.
pH 5 vs. pH 6 (10X more acidic) pH 3 vs. pH 5 (100X different)
pH 8 vs. pH 13 (100,000X different)
: measures acidity/basicity
10x 10x 10x 100x
Søren Sorensen (1868 - 1939)
Acid
Base
pH = -log [H1+]
pH = 7
Acidic Basic
Neutral
[H+] [OH-] [H+]
=
[OH-
]
Acid vs. Base
Acid
pH > 7
bitter
taste
does not
react with
metals
pH < 7
sour taste
react with
metals
Alike Different
Related
to
H+
(proton)
concentr
ation
pH +
pOH =
14
Affects
pH
and
litmus
paper
Base
Different
Topic Topic
Properties
• electrolytes
• turn litmus red
• sour taste
• react with metals to
form H2 gas
• slippery feel
• turn litmus blue
• bitter taste
ChemASAP
• vinegar, milk, soda,
apples, citrus fruits
• ammonia, lye, antacid,
baking soda
• electrolytes
Copyright © 2007 Pearson Benjamin Cummings. All rights reserved.
Common Acids and Bases
Strong Acids (strong electrolytes)
HCl hydrochloric acid
HNO3 nitric acid
HClO4 perchloric acid
H2SO4 sulfuric acid
Weak Acids (weak electrolytes)
CH3COOH acetic acid
H2CO3 carbonic
Strong Bases (strong
electrolytes)
NaOH sodium hydroxide
KOH potassium hydroxide
Ca(OH)2 calcium hydroxide
Weak Base (weak electrolyte)
NH3 ammonia
Kotz, Purcell, Chemistry & Chemical Reactivity 1991, page 145
Weak Base (weak electrolyte)
NH4OH ammonia
NH3 + H2O →
NH4OH
Acid-Base Neutralization
1+ 1
-
+ +
Hydronium ion Hydroxide ion
H3O+
OH-
Water
H2O
Water
H2O
Water
H2O
Water
H2O
Dorin, Demmin, Gabel, Chemistry The Study of Matter 3rd Edition, page 584
Acid-Base Neutralization
1+ 1-
+ +
Hydronium ion Hydroxide ion Water
H3O+ OH- H2O
Water
H2O
Dorin, Demmin, Gabel, Chemistry The Study of Matter 3rd Edition, page 584
Acid Rain
Acid Precipitation
http://nadp.sws.uiuc.edu/amaps2/
Formation of Sulfuric Acid
Kelter, Carr, Scott, Chemistry A World of Choices 1999, page 302
SO2(g) + H2O(l) H2SO3(aq)
2SO2(g) + O2(g) 2SO3(g)
SO3(g) + H2O(l) H2SO4(aq)
SO2(g) + H2O2(l) H2SO4(aq)
Catalyzed by atmospheric dust
Sulfuric acid
+
+
Acid Rain
Smoke stacks pollute SO2
into the atmosphere. This
combines with water to form
acid rain.
Estimated sulfate ion deposition, 1999
CO2 (g) H
2O (l) H
2CO
3 (aq)
Carbon
dioxide
Carbonic
acid
Water
Weak
acid
Copyright © 2007 Pearson Benjamin Cummings. All rights reserved.
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
Common Acids Formula Name of Acid Name of Negative
Ion of Salt
HF hydrofluoric fluoride
HBr hydrobromic bromide
HI hydroiodic iodide
HCl hydrochloric chloride
HClO hypochlorous hypochlorite
HClO2 chlorous chlorite
HClO3 chloric chlorate
HClO4 perchloric perchlorate
H2S hydrosulfuric sulfide
H2SO3 sulfurous sulfite
H2SO4 sulfuric sulfate
HNO2 nitrous nitrite
HNO3 nitric nitrate
H2CO3 carbonic carbonate
H3PO3 phosphorous phosphite
H3PO4 phosphoric phosphate
Formation of Hydronium Ions
1+
hydronium ion
H3O+
+
hydrogen ion
H+
water
H2O
1+
(a proton)
1+
Sulfuric Acid, H2SO4 Sulfuric acid is the most commonly produced industrial chemical in the world.
Uses: petroleum refining, metallurgy, manufacture of fertilizer,
many industrial processes: metals, paper, paint, dyes, detergents
Sulfuric acid is used in
automobile batteries.
H2SO4
“oil of vitriol”
Nitric Acid, HNO3
Nitric acid stains proteins yellow (like your skin).
Uses: make explosives, fertilizers, rubber, plastics, dyes, and pharmaceuticals.
HNO3
“aqua fortis”
O
O O
N H
Hydrochloric Acid, HCl
The stomach produces HCl to aid in the digestion of food.
Uses: For „pickling‟ iron and steel.
Pickling is the immersion of metals in acid solution to remove
surface impurities.
A dilute solution of HCl is called muriatic acid (available in many hardware
stores). Muriatic acid is commonly used to adjust pH in swimming pools
and in the cleaning of masonry.
HCl(g) + H2O(l) HCl(aq) hydrogen chloride water hydrochloric acid
Common Bases
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 NH3 H2O household ammonia
Name Formula Common Name
. NH4OH
NH41+ + OH1-
ammonium hydroxide
hydroxide
ion
OH1-
Common Bases
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 NH3 H2O household ammonia
Name Formula Common Name
. NH4OH
NH41+ + OH1-
ammonium hydroxide
hydroxide
ion
OH1-
Relative Strengths of Acids and Bases
perchloric HClO4
hydrogen chloride HCl
nitric HNO3
sulfuric H2SO4
hydronium ion H3O+
hydrogen sulfate ion HSO4-
phosphoric H3PO4
acetic HC2H3O2
carbonic H2CO3
hydrogen sulfide H2S
ammonium ion NH4+
hydrogen carbonate ion HCO3-
water H2O
ammonia NH3
hydrogen H2
Decre
asin
g A
cid
Str
ength
perchlorate ion ClO4-
chloride ion Cl-
nitrate ion NO3-
hydrogen sulfate ion HSO4-
water H2O
sulfate ion SO42-
dihydrogen phosphate ion H2PO4-
acetate ion C2H3O2-
hydrogen carbonate ion HCO3-
hydro sulfide ion HS-
ammonia NH3
carbonate ion CO32-
hydroxide ion OH-
amide ion NH2-
hydride ion H-
Decre
asin
g B
ase S
trength
Acid Formula Conjugate base Formula
Metcalfe, Williams, Catska, Modern Chemistry 1966, page
229
acid conjugate base + H+
Binary Hydrogen Compounds of Nonmetals When Dissolved in Water
(These compounds are commonly called acids.)
The prefix hydro- is used to represent hydrogen, followed by the name
of the nonmetal with its ending replaced by the suffix –ic and the word
acid added.
Examples:
*HCl
HBr
*The name of this compound would be hydrogen chloride if it was NOT dissolved in water.
Hydrochloric acid
Hydrobromic acid
Naming Ternary Compounds
from Oxyacids
The following table lists the most common families of oxy acids.
one more
oxygen atom
most
“common”
one less
oxygen
two less
oxygen
HClO4
perchloric acid
HClO3
chloric acid
HClO2
chlorous acid
HClO
hypochlorous acid
H2SO4
sulfuric acid
H2SO3
sulfurous acid
H3PO4
phosphoric acid
H3PO3
phosphorous acid
H3PO2
hypophosphorous acid
HNO3
nitric acid
HNO2
nitrous acid
(HNO)2
hyponitrous acid
An acid with a
name ending in
A salt with a
name ending in
-ic
-ous
-ate
-ite forms
forms
Hill, Petrucci, General Chemistry An Integrated Approach 1999, page
60
Oxyacids → Oxysalts
If you replace hydrogen with a metal, you have formed an oxysalt.
A salt is a compound consisting of a metal and a non-metal. If the
salt consists of a metal, a nonmetal, and oxygen it is called an
oxysalt. NaClO4, sodium perchlorate, is an oxysalt.
HClO4
perchloric acid
HClO3
chloric acid
HClO2
chlorous acid
HClO
hypochlorous acid
NaClO4
sodium perchlorate
NaClO3
sodium chlorate
NaClO2
sodium chlorite
NaClO
sodium hypochlorite
OXYACID OXYSALT
ACID SALT
per stem ic changes to per stem ate
stem ic changes to stem ate
stem ous changes to stem ite
hyper stem ous changes to hypo stem ite
HClO3 + Na1+ NaClO3 + H1+
acid cation salt
Arrhenius Acids and Bases
Acids release hydrogen ions in water.
Bases release hydroxide ions in water.
An acid is a substance that produces hydronium ions, H3O+,
when dissolved in water.
Lewis Definitions
A Lewis acid is a substance than can accept (and share) an electron pair.
A Lewis base is a substance than can donate (and share) an electron pair.
Lewis Acid
Brønsted-Lowry Definitions
A Brønsted-Lowry acid is a proton donor; it donates a hydrogen ion, H+.
A Brønsted-Lowry base is a proton acceptor; it accepts a hydrogen ion, H+.
Brønsted-Lowry
Arrh
eniu
s
acid
s
Acid Definitions
Acid Definitions
Lewis acids
Brønsted-Lowry
Arrhe
nius
acids
The Arrhenius model of acids
and bases was broadened by
the Brønsted-Lowry model.
The Lewis acid-base model is
the most general in scope.
The Lewis definition of an acid
includes any substance that
is an electron pair acceptor;
a Lewis base is any substance
that can act as an electron pair
donor.
Ralph A. Burns, Fundamentals of Chemistry 1999, page 483
Lewis acids
Brønsted-Lowry
Arrhe
nius
acids
The Arrhenius model of acids
and bases was broadened by
the Brønsted-Lowry model.
The Lewis acid-base model is
the most general in scope.
The Lewis definition of an acid
includes any substance that
is an electron pair acceptor;
a Lewis base is any substance
that can act as an electron pair
donor.
Ralph A. Burns, Fundamentals of Chemistry 1999, page 483
Acid Definitions
Acid – Base Systems
Type Acid Base
Arrhenius H+ or H3O +
producer
OH - producer
Brønsted-
Lowry
Proton (H +)
donor
Proton (H +)
acceptor
Lewis Electron-pair
acceptor
Electron-pair
donor
Arrhenius Acid
1+
+ +
hydronium ion
H3O+
1-
chloride ion
Cl-
water
H2O
hydrogen chloride
HCl
(an Arrhenius acid)
Any substance that releases H+ ions as the
only positive ion in the aqueous solution.
Definitions
◆Arrhenius - In aqueous solution…
HCl + H2O → H
3O
+ + Cl
–
• Acids form hydronium ions (H3O+)
H
H H H H
H
C
l
C
l
O O
– +
acid Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem
Definitions
◆Arrhenius - In aqueous solution…
• Bases form hydroxide ions (OH-)
NH3 + H
2O → NH
4
+ + OH
-
H
H
H H H
H
N N O O
– +
H
H
H H
base Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem
Arrhenius Bases and Their Properties
According to the definition of Arrhenius a:
Base - "a substance whose water solution yields...
Are NaOH and NH3 considered to be Arrhenius bases?
1) Bases are electrolytes
Dissociation equation for NH3
NH3(g) + H2O(l) NH41+(aq) + OH1-(aq)
Dissociation equation for NaOH
NaOH(s) Na1+(aq) + OH1-(aq)
2) Bases cause indicators to turn a characteristic color
3) Bases neutralize acids
NaOH(aq) + HCl(aq) NaCl(aq) + H2O(l)
YES
4) Water solutions of bases tasted bitter and feel slippery.
hydroxide ions (OH-) as the only negative ions."
Neutralization
Neutralization is a chemical reaction between an acid and a base
to produce a salt (an ionic compound) and water.
NaOH(aq) + HCl(aq) NaCl(aq) + H2O(l)
base acid salt water
Some neutralization reactions:
H2SO4(aq) + NaOH(aq) Na2SO4 + HOH
sulfuric acid sodium hydroxide sodium sulfate water
HC2H3O2(aq) + Ca(OH)2(aq) Ca(C2H3O2)2 + HOH
acetic acid calcium hydroxide calcium acetate water
2 2
2 2
Neutralization
ACID + BASE → SALT + WATER
HCl + NaOH → NaCl + H2O
HC2H
3O
2 + NaOH → NaC
2H
3O
2 + H
2O
• Salts can be neutral, acidic, or basic.
• Neutralization does not mean pH = 7.
weak
strong strong
strong
neutral
basic
Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem
ACID + BASE → SALT + WATER
HCl + NaOH → NaCl + H2O
HC2H
3O
2 + NaOH → NaC
2H
3O
2 + H
2O
• Salts can be neutral, acidic, or basic.
• Neutralization does not mean pH = 7.
weak
strong strong
strong
neutral
basic
Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem
Salts
Salts - Ionic compounds containing a positive ion other than the
hydrogen ion and a negative ion other than the hydroxide ion.
i.e., a metal and a non-metal
Under what conditions do salts conduct current?
NaCl(s) + H2O(l) Na1+(aq) + Cl1-(aq)
Formulas and names of common salts
SALT FORMULA Common Name
sodium chloride NaCl (table) salt
sodium nitrate NaNO3 Chile saltpeter
sodium bicarbonate NaHCO3 baking soda
potassium carbonate K2CO3 potash
ammonium chloride NH4Cl sal ammoniac
NaCl
Salt Formation
NaOH HCl
strong
base
strong
acid
salt of a strong base and a strong acid Na Cl
NaOH HC2H3O2
strong
base
weak
acid
salt of a strong base and a weak acid Na C2H3O2
Note: that in each case H-OH (water) is formed
NaOH + HCl → NaCl +
H2O
NaOH + HC2H3O2 → NaC2H3O2 + H2O
Salt Formation
NH3 H2SO4
weak
base
strong
acid
salt of a weak base and a strong acid (NH4) 2 SO4
NH3 HC2H3O2
weak
base
weak
acid
salt of a weak base and a weak acid NH4 C2H3O2
Note: that in each case H-OH (water) is also formed
NH4OH H2SO4
NH4OH + H2SO4 → (NH4)2SO4 +
H2O
NH4OH + HC2H3O2 → NH4C2H3O2 +
H2O
NH4OH
NH3 H2SO4
weak
base
strong
acid
salt of a weak base and a strong acid (NH4) 2 SO4
NH4OH H2SO4
ammonium
ion
NH4+
hydroxide
ion
OH-
1+ 1-
NH4+ OH-
1+ 1-
sulfuric
acid
(NH4)2SO4
HOH
1+
HOH
1+
sulfate ion
2 NH4OH + H2SO4 (NH4)2SO4 + 2
HOH water ammonium sulfate
2-
H2SO4
2 NH4OH + H2SO4 (NH4)2SO4 + 2
H2O
phosphoric acid ammonium hydroxide ammonium phosphate
Reactions that produce salt
acid + base salt + water
H3PO4 NH4OH (NH4)3PO4 H2O
nitric acid magnesium hydroxide magnesium nitrate
HNO3 Mg(OH)2 Mg(NO3)2 H2O
carbonic acid potassium hydroxide potassium carbonate
H2CO3 KOH K2CO3 H2O
acetic acid aluminum hydroxide aluminum acetate
HC2H3O2 Al(OH)3 Al(C2H3O2)3 H2O
perchloric acid barium hydroxide barium perchlorate
HClO4 Ba(OH)2 Ba(ClO4)2 H2O
+ + and yields and water
Brønsted-Lowry Acids and Bases
1+
+
hydronium ion
H3O+
1-
chloride ion
Cl-
(base)
H2O
(acid)
HCl
δ
+
δ
-
Acid = any substance that donates a proton.
Base = any substance that accepts a proton.
Brønsted-Lowry Acids and Bases
1+
+
hydronium ion
H3O+
1-
chloride ion
Cl-
(base)
H2O
(acid)
HCl
δ
+
δ
-
Acid = any substance that donates a proton.
Base = any substance that accepts a proton.
Brønsted-Lowry Acids and Bases
(acid)
H2O
(base)
NH3
δ
+
δ
-
1+
+
ammonium ion
NH4+
1
-
hydroxide
ion
OH-
Brønsted-Lowry Acids and Bases
1+
+
ammonium ion
NH4+
1-
hydroxide ion
OH-
(acid)
H2O
(base)
NH3
δ
+
δ
-
Brønsted-Lowry Acids and Bases
1+
+
ammonium ion
NH4+
1-
hydroxide ion
OH-
(acid)
H2O
(base)
NH3
δ
+
δ
-
Definitions
◆Brønsted-Lowry
HCl + H2O → Cl
– + H
3O
+
• Acids are proton (H+) donors.
• Bases are proton (H+) acceptors.
conjugate acid conjugate base
base acid
Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem
Definitions
H2O + HNO
3 → H
3O
+ + NO
3
–
CB CA A B
Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem
H
H
O H O
O
O
N
Base Acid
Definitions
◆Amphoteric - can be an acid or a base.
NH3 + H
2O → NH
4
+ + OH
-
CA CB B A
Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem
H
H
O
H
N
Base Acid
H
H
Definitions
F -
H2PO4-
H2O
HF
H3PO4
H3O+
◆ Give the conjugate base for each of the following:
◆Polyprotic - an acid with more than one H+
Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem
Definitions
Br -
HSO4-
CO32-
HBr
H2SO4
HCO3-
◆ Give the conjugate acid for each of the following:
Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem
Definitions
◆Lewis
• Acids are electron pair acceptors.
• Bases are electron pair donors.
Lewis base
Lewis acid
Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem
