PS
3.1a:
Substances have characteristic properties. Some of
room temperature,
density; solubility, heat
and
es
f:eeiiog
eiectrical conductivity,
section
and
Acidic
Basic Solutions
as you read
What makes orange
fruit tangy?
You'll
Compare
acids
Learn
and bases and
their properties.
Describe practical uses of acids
and bases.
Explain
how pH
is
used to describe
the strength of an acid or base.
how acids and bases
react when they are brought
Describe
Acids are substances that release positively charged hydrogen
ions,
+ in water. When an acid mixes with water, the acid
H
,
hydrogen ion. The hydrogen ion then
combines with a water molecule to form a hydronium ion, as
dissolves, releasing a
shown in Figure 14. Hydronium ions are positively charged and
have the formula H30+.
Properties of Acidic Solutions Sour
together.
properties of acidic solutions.
It's
Many common
batteries
Important
The
and bleach, work because
identify acidic solutions
taste
by
their sour taste,
one of the
to detect the
you can
you should never
taste
an unknown substance. Many
burns to body tissues.
Another property of acidic solutions is that they can conduct
acids can cause serious
physical property: any character-
of a material that can be
electricity.
The hydronium
ions in an acidic solution can carry
seen or measured without chang-
the electric charges in a current. This
ing the material
tain
an
is
why some batteries
acid. Acidic solutions also are corrosive,
con-
which means
they can break down certain substances. Many acids can corrode
New Vocabulary
fabric, skin,
e pH
e indicator
and paper. The solutions of some acids
strongly with certain metals.
neutralization
ion
you
anything in the laboratory, and you should never use
to test for the presence of acids in
Review Vocabulary
e acid
e hydronium
taste is
taste allows
presence of acids in your food. However, even though
products, such as
of acids or bases.
iStic
and grape-
juice, vinegar, dill pickles,
Acids cause the sour taste of these and other foods.
metallic
e base
The acid-metal
compounds and hydrogen
also react
reaction forms
gas, leaving holes in the
metal in the process.
H20
Figure 14 One hydrogen
1-130
ion
can combine with one water mole-
0+
cule to form one positively charged
hydronium
ion.
Identify what kinds of substances
are sources of hydrogen ions.
Hydrogen
ion
Substances, Mixtures, and Solubility
Water
Hydronium
molecule
ion
Figure 15
ucts contains
Each of these prod-
an acid or
is
made
with the help of an acid.
Describe
how your life would be
were not available
different ifacids
to
make these products.
The Béttgr Battery.
1
f
6 Volt
Lantern.
e utter
Uses Of Acids
which
Vinegar,
is
many
You're probably familiar with
y
acids.
Mini
used in salad dressing, contains acetic acid.
Lemons, limes, and oranges have a sour taste because they contain
citric acid.
Your body needs ascorbic
acid,
which
is
vitamin C.
Ants that sting inject formic acid into their victims.
Figure 15 shows other products that are
Sulfuric acid
and
plastics.
tions
is
used in the production of fertilizers,
electricity.
to as battery acid.
Pickling
For
this reason,
brick walls. Nitric acid
and
steel, paints,
sometimes
is
is
is
known commer-
is
1.
used in the production of
Observe the
initial
appearance of an iron nail.
2. Pour
enough carbonated
soft drink into a cup or
used in a process called pickling.
from the surfaces of
can be used to clean mortar from
so
Procedure
referred
a process that removes impurities
metals. Hydrochloric acid also
dyes,
it
Hydrochloric acid, which
muriatic acid,
is
acids.
Acids often are used in batteries because their solu-
conduct
cially as
made with
Observing a Nail in a
Carbonated Drink
beaker to cover the
3.
Drop the
drink
fertilizers,
nail into
and observe what
happens.
4. Leave the nail in the soft
plastics.
drink overnight
it
the Environment Carbonic acid plays a key role in
and of stalactites and stalagmites.
Carbonic acid is formed when carbon dioxide in soil is dissolved
Acid
and observe
again the next day.
in
the formation of caves
When
Analysis
1. Describe
this acidic solution
nail into
acid rain
falls
on
When
statues
and
eats
away
at the stone, as
from the ceiling of
the cave, water evaporates and carbon dioxide becomes less soluble, forcing it out of solution. The solution becomes less acidic
and the limestone becomes less soluble, causing it to come out
Of solution. These solids form stalactites and stalagmites.
Figure 16.
this acidic solution drips
first
dropped the
the soft drink
and
the appearance of the nail
carving out a cave in the rock. A similar process occurs
when
shown in
what happened
when you
comes in contact with calcium carbonate—or limestone rock—it can dissolve it, eventuin water.
ally
nail.
the soft
the following day.
2.
Based upon the fact that
the soft drink
was
carbonated, explain why
you think the drink reacted
with the
nail
as you
observed.
Acidic
and
Basic Solutions
Bases
people often use
ammonia
solutions to clean
windows and
from those of
These solutions have different properties
acidic solutions. Ammonia is called a base. Bases are sub-
floors.
hydrogen
stances that can accept
attracted to the base.
leaves
A
tain a
A
When
bases dissolve in
the water molecules are
hydrogen atom in the water molecule
behind the other hydrogen atom and oxygen atom. This
atoms
pair of
ion.
ions.
some hydrogen atoms from
water,
a negatively charged ion called a hydroxide
hydroxide ion, which
formula
released
is
OH¯. Most
when
For example, sodium hydroxide
bases con-
Web
is
a base with the
dissolves in water, a
soap
Activity Describe the chemical
sodium ion
feels,
(calcium carbonate) to calcium
hydroxide.
Properties of Basic Solutions Most soaps
how
calcium hydroxide.
reaction that converts limestone
NaOH. When NaOH
you think about
links
to information about the uses for
the base dissolves
and the hydroxide ion separate.
if
Topic: Calcium Hydroxide
Visit
is
hydroxide ion has the formula
in water.
nline
Scienc
you can
are bases, so
figure out
some of
the properties of basic solutions. Basic solutions feel slippery.
Acids in water solution taste sour, but bases taste bitter—
as
you know
if
you have ever accidentally gotten soap
in
your mouth.
Like acids, bases are corrosive. Bases can cause burns
damage
tissue.
find out
You should never touch or
whether
can conduct
and
taste a substance to
a base. Basic solutions contain ions and
it is
electricity.
Basic solutions are not as reactive with
metals as acidic solutions are.
Uses Of Bases Many uses
Bases give soaps,
some of
for bases are
shown
in Figure 17.
ammonia, and many other cleaning products
The hydroxide ions produced
their useful properties.
by bases can interact strongly with certain substances, such as
Figure 17 Many
products,
including soaps, cleaners, and plas-
and grease.
Chalk and oven cleaner are examples of familiar products
that contain bases. Your blood is a basic solution. Calcium
dirt
ter contain bases or are
made with
the help of bases.
hydroxide, often called lime,
is
used to mark the lines on
athletic fields. It also
can be
used to treat lawns and gar-
dens that have acidic
soil.
Sodium hydroxide, known
lye, is
as
a strong base that can
fAMiLY
stu
MONIA
WE
cause burns and other health
opr
problems. Lye
make
is
used to
soap, clean ovens,
oz. (101.)
yaw
e
QHALK
and
unclog drains.
Acidic
and
Basic Solutions
What
pH?
is
You've probably heard of pH-balanced
and you might have seen someone test the pH of the water
in a swimming pool. pH is a measure of how acidic or basic a
solution is. The pH scale ranges from 0 to 14. Acidic solutions
have pH values below 7. A solution with a pH of 0 is very acidic.
ant,
pH Levels Most life-forms
can't exist at extremely
low pH
levels.
However,
some bacteria thrive
in
acidic environments.
Hydrochloric acid can have a
Acidophils are bacteria
is
pH levels.
that exist at low
with
it is
neither acidic nor basic. Pure water
is
pH values above 7. A solution with
pH of 14 is very basic. Sodium hydroxide can have a pH of 14.
Figure 18 shows where various common substances fall on the
pH scale.
The pH of a solution is related directly to its concentrations
pH levels
1
meaning
a
Yellowstone National Park
ranging from
neutral,
pH of 0. A solution with a pH of 7
neutral. Basic solutions have
These bacteria have been
found in the Hot Springs of
in areas
shampoo or deodor-
to 3.
of hydronium ions (H30+) and hydroxide ions (OH¯). Acidic
solutions have
more hydronium ions than hydroxide
ions.
Neutral solutions have equal numbers of the two ions. Basic
solutions have
more hydroxide
In
hydronium
ions than
a neutral solution,
ions.
how do the numbers of
hydronium ions and hydroxide ions compare?
pH Scale The pH scale is not a simple linear scale like mass or
one book has a mass of 2 kg and a second book has a mass of 1 kg, the mass of the first book is twice
volume. For example,
if
that of the second. However, a change of
1
pH unit represents a
tenfold change in the acidity of the solution. For example,
solution has a
first
solution
one
pH of I
is
and a second solution has a pH of 2, the
not twice as acidic as the second—it is ten times
To determine the difference in pH strength, use the
1071, where n
the difference between
100 times more acidic.
pHs. For example: pH3 — PHI
2, 102
more
Figure 18 The pH
if
acidic.
following calculation:
scale classi-
fies a solution as acidic, basic,
or neutral.
Egg white
Vinegar
Milk
Gastric contents
Hydrochloric
acid
1
2
3
4
5
7
6
Sodium hydroxide
Baking
soda
8
Ammonia
9
10
11
Milk of
Blood plasma
Soft drinks
Tomatoes
Substances, Mixtures, and Solubility
magnesia
12
13
14
Figure 19
Acetic Acid
Hydrochloric Acid
Hydrochloric acid
separates into ions
more
than acetic acid does
readily
when
it
dissolves in water. Therefore,
hydrochloric acid exists in water as
separated ions. Acetic acid exists
water almost
_
entirely as molecules.
Acetate ion
Acetic acid
ion
Strengths of Acids and Bases You've learned that acids
give foods a sour taste but also can cause burns and damage tissue. The difference between food acids and the acids that can
burn you is that they have different strengths. The acids in food
are fairly weak acids, while the dangerous acids are strong acids.
is related to how easily the acid separates
how easily a hydrogen ion is released, when the acid
The strength of an acid
into ions, or
Look
dissolves in water.
at Figure 19. In the
same concentra-
Physical Setting
3.1a, 3.2c Design a chart to
tion, a strong
acid—like hydrochloric acid—forms more hydronium ions in solution than a weak acid does—like acetic acid.
compare acids to bases. Include
More hydronium ions means
water, general physical and
lower
the strong-acid solution has a
pH than the weak-acid solution. Similarly, the strength of
a base
is
related to
how
how each reacts chemically to
chemical characteristics, and
neutralization.
easily the base separates into ions, or
how easily a hydroxide ion is released, when the base dissolves in
water.
are
The
shown
relative strengths
of some
common
acids
and bases
in Table 3.
Whatdetermines the strength ofan acidora base?
An
acid containing
more
hydrogen atoms, such as carbonic acid, H2C03,
essarily stronger
is
.
acid's strength
how
easily a
Base
Acid
than an acid
Strong
hydrochloric (HCI)
sodium hydroxide (Na0H)
sulfuric (H2S04)
potassium hydroxide (KOH)
is
nitric
related to
Some Acids and Bases
not nec-
containing fewer hydrogen
atoms, such as nitric acid,
HNO An
Table 3 Strengths of
(HN03)
hydro-
gen ion separates—not to
how
many hydrogen atoms
has.
it
For this reason, nitric acid
is
Weak
acetic
(CH3COOH)
ammonia
(NH3)
carbonic (H2C03)
aluminum hydroxide
ascorbic (H2C6H606)
iron
(Ill)
hydroxide
stronger than carbonic acid.
Acidic
in
and Basic Solutions
Indicators
way to find out how acidic or basic a solution
is? Indicators are compounds that react with acidic and basic
solutions and produce certain colors, depending on the solu-
What
•
tion's
is
a safe
PH.
Because they are different colors at different pHs, indicators
Scienconline
can help you determine the
Topic: Indicators
such as litmus, are soaked into paper
for
Visit
Web
links to
information about the types of pH
indicators.
is
pH
placed in an acidic solution,
of a solution.
it
Some
indicators,
When litmus paper
red. When placed in a
strips.
turns
basic solution, litmus paper turns blue.
Some
indicators can
change through a wide range of colors, with each different color
Activity Describe how
can act as indicators
plants
in acidic
appearing at a different
pH value.
and
basic solutions.
Neutralization
Perhaps you've heard someone complain about heartburn or
an upset stomach after eating spicy food. To feel better, the person might have taken an antacid. Think about the word antacid
How do antacids work?
Heartburn or stomach discomfort
for a minute.
is
caused by excess
hydrochloric acid in the stomach. Hydrochloric acid helps break
down
the food
you
eat,
but too
much
of
it
can
irritate
your
stomach or digestive tract. An antacid product, often made from
the base
magnesium hydroxide, Mg(OH)2, neutralizes the excess
acid. Neutralization
Figure 20 The pH ofa
is
more
acidic
when
solution
(new truh luh ZAY shun)
is
the reaction of
an acid with a base. It is called this because the properties of
both the acid and base are diminished, or neutralized. In most
cases, the reaction produces a water and a salt. Figure 20 illus-
greater
amounts of hydronium
ions are
trates the relative
between
present.
amounts of hydronium and hydroxide ions
pH 0 and pH
14.
Define what makes a pH 7 solution
neutral.
14
Substances, Mixtures, and Solubility
2+120
1-130
Figure 21 When
basic solutions react,
acidic
and hydroxide
and
hydronium
ions react to
form
water.
Determine why the pH of the
solution changes.
Hydronium
Hydroxide
ion
ion
Water molecules
How does
neutralization occur? Recall that every water
molecule contains two hydrogen atoms and one oxygen atom.
As Figure 21 shows, when one hydronium ion reacts with one
hydroxide ion, the product
is
two water molecules. This reaction
occurs during acid-base neutralization. Equal numbers of
hydronium ions from the acidic solution and hydroxide ions
from the basic solution react to produce water. Pure water has a
pH of 7, which means that it's neutral.
Reading Chekk- What happens to acids and bases during
neutralization?
review
section
Summary
Acids
Self Check
and Bases
1. Identify
0 Acids are substances that
charged hydrogen ions
• Substances
in
release positively
bases
water.
bases.
that accept hydrogen ions
2.
in
what
ions are produced by acids in water and
water. Give
two
Name three acids and three
3. Explain
and basic solutions can conduct
bases and
list
an
industrial
how the
concentration of hydronium ions and
hydroxide ions are related to PH.
electricity.
4.
Think
what ways might
Critically In
uses a strong acid handle an acid
pH
a
spill
company that
on the factory
floor?
0 pH measures how
acidic or basic a solution
is.
Hot Words Hot Topics. Bk 2
• The
properties each of acids and
or household use of each.
water are bases.
Acidic
in
scale ranges
(5)
pp. 91, 169
from 0 to 14.
Applying Math
Neutralization
0
Neutralization
acid
and
5.
is
the interaction between an
a base to
form water and a
More Section Review
salt.
Solve One-Step Equations
solution with a
pH
much more basic
with a pH of 10?
How much more acidic is a
pH of 6? How
of 2 than one with a
is
a solution with a
Acidic
and
pH of 13 than one
Basic Solutions