© 2003 John Wiley and Sons Publishers
Chapter 10: Acids and Bases
Courtesy Susan Johns/Photo Researchers
If It Tastes Sour It Must Be An Acid
© 2003 John Wiley and Sons Publishers
Courtesy Andy Washnik
Figure 10.1: The red cabbage breath test. (a) Heating leaves of red cabbage in water to
extract the acid-base indicator that gives the cabbage its color.
© 2003 John Wiley and Sons Publishers
Courtesy Andy Washnik
Figure 10.2: Acids turn blue litmus red. Bases turn red litmus blue.
© 2003 John Wiley and Sons Publishers
Courtesy Robert J. Capece
Acids and bases in consumer products. Some are hazardous and must be used with
care.
© 2003 John Wiley and Sons Publishers
Courtesy Andy Washnik
Pieces of zinc metal react with hydrochloric acid to produce hydrogen gas.
Acids
 Arrhenius acids
 Produce H+ ions in water.
H2O
HCl
H+(aq) + Cl– (aq)
 Are electrolytes.
 Have a sour taste.
 Corrode metals.
 React with bases to form salts
and water.
© 2003 John Wiley and Sons Publishers
Courtesy Elliot V. Fry/AIP Emilio Segre
Visual Archives
Svante August Arrhenius defined an acid as anything that produces hydrogen ions in
water.
Bases
 Arrhenius bases
 Produce OH– ions in
water.
 Taste bitter or chalky.
 Are electrolytes.
 Feel soapy and slippery.
 React with acids to
form salts and water.
Comparing Acids and Bases
Learning Check
Identify each as a characteristic of an
A) acid
or
B) base
____1. Has a sour taste.
____2. Produces OH- in aqueous solutions.
____3. Has a chalky taste.
____4. Is an electrolyte.
____5. Produces H+ in aqueous solutions.
Solution
Identify each as a characteristic of an
A) acid or B) base
A
1. Has a sour taste.
B
2. Produces OH– in aqueous solutions.
B
3. Has a chalky taste.
A, B 4. Is an electrolyte.
A
5. Produces H+ in aqueous solutions.
Some Acids and Their Anions
Some Common Bases
 Bases with OH- ions are named as the
hydroxide of the metal in the formula.
NaOH
KOH
Ba(OH)2
Al(OH)3
Fe(OH)3
sodium hydroxide
potassium hydroxide
barium hydroxide
aluminum hydroxide
iron (III) hydroxide
BrØnsted-Lowry Acids and Bases
According to the Brønsted-Lowry theory,
• Acids are hydrogen ion (H+) donors.
• Bases are hydrogen ion (H+) acceptors.
donor
acceptor
hydronium ion
HCl
+
H2 O
H3O+ + Cl+
+
+
© 2003 John Wiley and Sons Publishers
Courtesy Edger Fahs Smith
Collection/University of Pennsylvania
Johannes Brønsted.
NH3, A Bronsted-Lowry Base
• When NH3 dissolves in water, a few NH3
molecules react with water to form ammonium
ion NH4+ and a hydroxide ion.
NH3 + H2O
NH4+(aq)
+ OH- (aq)
acceptor donor
+
+
+
-
© 2003 John Wiley and Sons Publishers
Courtesy Andy Washnik
Figure 10.3: Vapors of ammonia and hydrogen chloride combine above the bottles to
form ammonium chloride, which appears as a fog.
© 2003 John Wiley and Sons Publishers
Courtesy Charles D. Winters/Photo
Researchers
Figure 10.6: A pH meter, an instrument used for the very accurate measurement of
hydrogen ion concentrations.
Review
BrØnsted-Lowry Acids and Bases
According to the Brønsted-Lowry theory,
• Acids are hydrogen ion (H+) donors.
• Bases are hydrogen ion (H+) acceptors.
donor
acceptor
hydronium ion
HCl
+
H2 O
H3O+ + Cl+
+
+
pH Scale
The pH scale:
 Is used to indicate the acidity of a solution.
 Has values that usually range from 0 to 14.
 Indicates an acidic solution when the values
are less than 7.
 Indicates a neutral solution with a pH of 7.
 Indicates a basic solution when the values
are greater than 7.
pH Range
0
1
2
3
4
5
6
7
8 9 10 11 12 13 14
Basic
Acidic
[H3O+]>[OH-]
Neutral
[H3O+] = [OH-]
[H3O+]<[OH-]
Learning Check
Identify each solution as
1. acidic
2. basic
3. neutral
A. ___ HCl with a pH = 1.5
B. ___ Pancreatic fluid pH = 8
C.___ Sprite soft drink pH = 3.0
D. ___ pH = 7.0
Solution
Identify each solution as
1. acidic
2. basic
3. neutral
A. 1 HCl with a pH = 1.5
B. 2
Pancreatic fluid
C. 1
Sprite soft drink pH = 3.0
D. 3 pH = 7.0
Testing the pH of Solutions
• The pH of solutions can be determined using a
a) pH meter, b) pH paper, and c) indicators
that have specific colors at different pHs.
© 2003 John Wiley and Sons Publishers
Courtesy Ken Karp
Figure 10.7: Common acids include the citric acid of limes, lemons, oranges, grapefruit,
and citrus juices, the propionic acid of Swiss cheese, and the oxalic acid of rhubarb.
© 2003 John Wiley and Sons Publishers
Courtesy Miles Laboratories
Carbon dioxide is released when an Alka-Seltzer tablet is dropped into water.
© 2003 John Wiley and Sons Publishers
Courtesy Andy Washnik
Figure 10.1 (b): Pouring out the solution of the indicator.
© 2003 John Wiley and Sons Publishers
Courtesy Andy Washnik
Figure 10.1 (c): Adding just enough dilute ammonia to turn the indicator solution green.
© 2003 John Wiley and Sons Publishers
Courtesy Andy Washnik
Figure 10.1 (d,e): Blowing into the slightly basic solution to make it slightly acidic and
turn its color from green to blue.
© 2003 John Wiley and Sons Publishers
Courtesy Andy Washnik
Figure 10.1 (f): Adding vinegar turns the blue solution pink.
© 2003 John Wiley and Sons Publishers
Figure 10.8: Le Châtelier’s Principle in operation.
© 2003 John Wiley and Sons Publishers
Figure 10.9: The chemistry of the fizz.
QUESTION
© 2003 John Wiley and Sons Publishers
What is the color of litmus paper when its
moistened (a) with ammonia? (b) with vinegar?
QUESTION
© 2003 John Wiley and Sons Publishers
Write balanced equations to show how each of
the following salts can be produced by the
reaction of an acid with a base: (a) K2SO4 (b)
CaI2, and MgCO3.
QUESTION
© 2003 John Wiley and Sons Publishers
Is it possible for a base to exist in the absence
of an acid (a) in terms of the Arrhenius
definition? (b) in terms of the Brønsted-Lowry
definition? Explain.
QUESTION
© 2003 John Wiley and Sons Publishers
Recognizing that free hydrogen ions do not
exist in water, complete the chemical equation
for the ionization of HCl in water:
HCl + H2O  Cl- = ?
QUESTION
© 2003 John Wiley and Sons Publishers
Suppose you have a solution of HCl in water
that has a hydronium ion concentration of
[H3O+] = 0.0001 M. Write this hydronium ion
concentration in exponential notation. Now
suppose you have a solution in which [H3O+] =
10-5. Write the hydronium ion concentration of
this solution in conventional, decimal notation.
QUESTION
© 2003 John Wiley and Sons Publishers
Which member (if either) of each of the
following pairs would you expect to show a
higher hydronium ion concentration: (a) 0.01 M
HCl or 0.0001 M HCl; (b) 0.01 M acetic acid or
0.0001 M acetic acid; (c) 0.01 M HCl or 0.0001
M acetic acid; (d) 0.01 M HCl or 0.01 M acetic
acid?
QUESTION
© 2003 John Wiley and Sons Publishers
(a) A typical pH for household ammonia is 11.
To what value of [H3O+] does this correspond?
(b) What is the value of [OH-] in household
ammonia? (c) The hydronium ion
concentration of an average tomato is about
0.001 M . What is the pH of the average
tomato?
QUESTION
© 2003 John Wiley and Sons Publishers
Name or identify each of the following
carboxylic acids: (a) gives rancid butter its
foul odor; (b) toxic, it is found in small
concentrations in raw spinach and rhubarb; (c)
forms in our muscles as a result of metabolic
activity; (d) produces the flavor of Swiss
cheese; (e) used as its sodium salt to preserve
canned and bottled fruit drinks (f) responsible
for the taste of sour milk; (g) produces the
acidity of citrus fruit; (h) generates the sting of
red ant bites; (i) the major organic acid of
vinegar.
QUESTION
© 2003 John Wiley and Sons Publishers
Some commercial antacids claim only to
neutralize “excess” stomach acidity. Why is it
undesirable to neutralize completely all
stomach acidity? What would result from
bringing the pH of stomach fluids all the way
up to 7?
QUESTION
© 2003 John Wiley and Sons Publishers
Hyperventilation, which occurs with very rapid
and very deep breathing, results in a rapid
loss of carbon dioxide from the body through
the lungs. What happens to the pH of the
blood as the direct result of hyperventilation?
Does the pH immediately rise or drop or does
it remain unchanged? Explain.