Chemistry for Changing Times
11th Edition
Hill and Kolb
Chapter 7
Acids and Bases
John Singer
Jackson Community College, Jackson, MI
© 2007 Prentice Hall
Acids and Bases: Experimental
Definitions
Acids:
taste sour
turn litmus red
react with active metals to release hydrogen gas
react with bases to form water and a salt
Acids and Bases: Experimental
Definitions
Bases:
taste bitter
turn litmus blue
feel slippery
react with acids to form water and a salt
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Acids and Bases: Experimental
Definitions
Acids, Bases, and Salts
Arrhenius Theory
Acid: a molecular substance that ionizes in aqueous
solution to form hydrogen ions (H+)
Acids, Bases, and Salts
Arrhenius Theory
Base: a substance that produces hydroxide ions (OH-)
in aqueous solution
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Acids, Bases, and Salts
Neutralization: When an acid reacts with a
base, the properties of each are
neutralized and the products are water
and a salt.
Acid + Base → Water + Salt
Acids, Bases, and Salts
Limitations of the Arrhenius Theory
- H+ ions do not exist in water solution. Protons
react with water to form hydronium ions. (H3O+)
H+ + H2O → H3O+
- The Arrhenius Theory does not explain the
basicity of ammonia and similar compounds.
- It only applies to reactions in aqueous solution.
Acids, Bases, and Salts
Brønsted-Lowry Theory
Acid: proton donor
HA + H2O → H3O+ + ABase: proton acceptor
NH3 + H2O → NH4+ + OH-
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Acids, Bases, and Salts
Brønsted-Lowry Theory
Acidic and Basic Anhydrides
Anhydride means without water.
Nonmetal oxides are acidic anhydrides.
SO3 + H2O → H2SO4
Acidic and Basic Anhydrides
Metal oxides are basic anhydrides.
Example:
Lime (calcium oxide) reacts with water to form
slaked lime (calcium hydroxide).
CaO + H2O → Ca(OH)2
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Strong and Weak Acids and Bases
Strong acids ionize completely in water
solution.
100%
HCl(aq) → H+(aq) + Cl-(aq)
Weak acids only partially ionize in water
solution.
HCN(aq) ↔ H+(aq) + CN-(aq)
Strong and Weak Acids and Bases
Strong bases ionize completely in water
solution.
100%
NaOH(aq) → Na+(aq) + OH-(aq)
Weak bases only partially ionize in water
solution.
NH3(aq) + H2O ↔ NH4+(aq) + OH-(aq)
Strong and Weak Acids and Bases
Ammonia accepts a proton from water forming
a basic solution.
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Neutralization
The reaction of an acid with a base is
called neutralization. Water molecules
are the result of the reaction between
hydrogen ions and hydroxide ions.
H+ + OH- ↔ H2O
Neutralization
During neutralization, an acid reacts with a
base, forming water and a salt.
Neutralization
The amount of acid (or base) in a solution is
determined by careful neutralization.
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The pH Scale
pH is a means of expressing the acidity or
basicity of a solution.
The pH Scale
pH means “power”
of hydrogen.
pH = -log[H+]
The pH Scale
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Acid Rain
Nonmetal oxides present in air react with
water, forming acidic solutions. Rain with
a pH of less than 5.6 is considered to be
acid rain. Carbon dioxide (CO2), sulfur
dioxide (SO2), nitrogen monoxide (NO),
and nitrogen dioxide (NO2) are the major
nonmetallic oxides responsible for acid
rain formation.
Antacids: A Basic Remedy
Hyperacidity is when the stomach
secretes too much acid. Antacids are
often taken to neutralize excess acid and
reduce the symptoms of hyperacidity.
Excessive use of antacids can lead to an
increase in the pH of blood, a condition
known as alkalosis.
Antacids: A Basic Remedy
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Antacids: A Basic Remedy
Substance
Formula
Product(s)
sodium
bicarbonate
calcium
carbonate
aluminum
hydroxide
magnesium
hydroxide
NaHCO3
baking soda
CaCO3
Tums®
Al(OH)3
Amphojel®
Mg(OH)2
Milk of
Magnesia®
Acids and Bases in Industry and at
Home
Sulfuric acid is the leading chemical
substance produced in the U.S. It is used
to manufacture fertilizers and industrial
chemicals. It is the acid of automotive
batteries. Production is 40 billion kg/year.
Acids and Bases in Industry and at
Home
Hydrochloric acid has a number of uses.
It is used as a rust remover, it removes
lime from mortar and household plumbing
fixtures. It can be purchased from
hardware stores as muriatic acid. Annual
U.S. production is 4 billion kg.
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Acids and Bases in Industry and at
Home
Lime (CaO) is produced by heating
limestone (CaCO3).
CaCO3 + heat → CaO + CO2
Lime can be slaked by reacting with water
to make calcium hydroxide (Ca(OH)2).
Slaked lime is used to make mortar and
cement and to sweeten soil. Annual U.S.
production is 22 billion kg.
Acids and Bases in Industry and at
Home
Soil can be “sweetened” by adding
slaked lime [Ca(OH)2].
Acids and Bases in Industry and at
Home
Sodium hydroxide, also known as lye,
can be purchased for home use as oven
cleaner or drain cleaners. It is used
commercially to make soap. Annual U.S.
production is 9 billion kg.
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Acids and Bases in Industry and at
Home
Ammonia is produced for use as fertilizer
and in household cleaning products.
Production is about 11 billion kg/year.
Acids and Bases in Health and
Disease
Concentrated acids and bases are
corrosive to tissue and are health hazards.
They can denature proteins in living cells.
The human body has wonderful
mechanisms for maintaining the proper pH
of tissue, blood, and body fluids.
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