Acids and Bases
Definitions of Acids
 Arrhenius Acid-any substance that
produces hydrogen ions (H+) when
dissolved in water.
 Bronsted Lowry acid-any substance
that donates protons to form
hydronium ions (H3O+)
 Examples of acids: HCl, HNO3, H2SO4,
HC2H3O2
Electrolytes
 Solutions that conduct an electric
current efficiently contain strong
electrolytes.
 Strong electrolytes are substances
that completely ionize in water.
 Acids that ionize completely and are
classified as strong electrolytes are
also classified as strong acids.
Strong acids
 The following are classified as strong
acids:
 HCl, HBr, HI, H2SO4, HNO3,HClO3, HClO4
 All other acids are classified as weak
acids (they do not ionize completely
in water).
 Note: a classification of strong vs weak acid is
independent of the concentration-for example,
a strong acid can be very dilute and a weak
acid can be very concentrated.
Properties of Acids
 Taste sour
 React with metals
 Conduct electricity (to some degree
based on strength)
 pH<7
 Turn litmus red
 Turn phenolphthalein colorless
Definitions of Bases
 Arrhenius Base-any substance that
produces hydroxide ions (OH-) when
dissolved in water.
 Bronsted Lowry Base- any substance
that accepts protons.
 Examples of bases: NaOH, Ca(OH)2,
Mg(OH)2, NH3
Bases as electrolytes
 Bases are also classified as strong vs
weak, based on the degree of
ionization.
 The strong bases (strong electrolytes) are:
(group 1A hydroxides, Sr(OH)2 and
Ba(OH)2 )
 All other bases are classified as weak
bases.
Properties of Bases






Taste bitter
Feel slippery
Conduct electricity
pH>7
Turn litmus blue
Turn phenolphthalein pink
NaOH is an example of a(n)
1. Acid
2. Base
3. Neither
0%
0%
0%
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A substance that is a proton
acceptor is a(n)
1. Acid
2. Base
3. neither
0%
0%
0%
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HCl is an example of a(n)
1. Acid
2. Base
3. Neither
0%
0%
0%
10
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Lemon juice is an example of a(n)
1. Acid
2. Base
3. Neither
0%
0%
0%
10
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A substance that is a proton donor
is an example of a(n)
1. Acid
2. Base
3. Neither
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0%
0%
10
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Drain cleaner is an example of a(n)
1. Acid
2. Base
3. Neither
0%
0%
0%
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Vinegar is an example of a(n)
1. Acid
2. Base
3. Neither
0%
0%
0%
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Water is an example of a(n)
1. Acid
2. Base
3. Neither
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0%
0%
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A substance that turns litmus red is
a(n)
1.
2.
3.
4.
0%
0%
0%
0%
Acid
Base
Neither
Both
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A substance that conducts
electricity is a(n)
1.
2.
3.
4.
0%
0%
0%
0%
Acid
Base
Neither
Both
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Naming Acids
 Binary acids- consist of hydrogen and
one other element.
 Use the prefix –hydro and change the
ending of the element to –ic.
 Example: HCl hydrochloric acid
HBr hydrobromic acid
H2S hydrosulfuric acid
Naming acids
 Oxyacids-consist of hydrogen, oxygen, and
one additional element.
 If the polyatomic ion ends in –ate, change
the ending to –ic.
 If the polyatomic ion ends in –ite, change
the ending to –ous.
 Example: H2SO4 sulfuric acid (diprotic)
H2SO3
sulfurous acid (diprotic)
HNO3
nitric acid (monoprotic)
HNO2 nitrous acid (monoprotic)
H3PO4
phosphoric acid (triprotic)
Naming bases
 All bases consist of the hydroxide ion
and one additional element.
 Name the element followed by
hydroxide.
 Example: NaOH sodium hydroxide
Ca(OH)2 calcium hydroxide
Al(OH)3 aluminum hydroxide
Which of the following is the
correct name of HBr?
1.
2.
3.
4.
0%
0%
0%
0%
10
Hydrobromic acid
Bromic acid
Bromous acid
Bromine hydroxide
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10
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Which of the following is the
correct name of H2CO3?
1.
2.
3.
4.
0%
0%
0%
0%
10
Hydrocarbonic acid
Carbonic acid
Carbonous acid
Hydrogen coarbon oxide
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Which of the following is the
correct name of Ba(OH)2?
1.
2.
3.
4.
0%
0%
0%
0%
10
Hydrobaric acid
Baric acid
Barous acid
Barium hydroxide
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pH Scale
Calculating pH
 The pH scale is a logarithmic scale
used to quantitatively represent the
strength (concentration) of an acid.
 pH = -log[H+] or pH = -log[H3O+]
 The greater the concentration of the
hydrogen ion (H+) or the hydronium
ion (H3O+), the stronger the acid and
the lower the pH.
Sample Problems
 What is the pH of a solution in which
[H+] = 1 x 10-2?
 pH = 2
 What is the pH of a solution in which
[H+] = 1 x 10-6?
 pH = 6
 Which is more concentrated?
 pH=2
pH and pOH
 The pOH scale is a logarithmic scale
used to quantitatively represent the
strength (concentration) of a base.
 pOH = -log[OH-]
 The greater the concentration of the
hydroxide ion (OH-), the stronger the
base and the lower the pOH.
 pOH + pH = 14
Practice Problems
 Calculate the pH and pOH of solutions
with the following concentrations and
classify as acidic, basic, or neutral.
a. [OH-] = 1 x 10-9
b. [H+] = 1 x 10-7
c. [H+] = 1 x 10-4
d. [OH-] = 1 x 10-2
Indicators and pH
 Indicators are substances that change
color depending on the concentration
of hydrogen ions (H+) in a solution.
 Litmus and phenolphthalein are
examples of indicators.
 Indicators can be used to determine
the pH of a solution.
 http://www.explorelearning.com/
A solution with a pH of 3 is
10
1. Acidic
2. Basic
3. Neutral
0%
0%
0%
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Which of the following is an expected
pH for a sample of lemon juice?
10
1.
2.
3.
4.
0%
0%
0%
0%
3
6
7
10
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A substance with a pH of 12.7 is
a(n)
1.
2.
3.
4.
0%
0%
0%
0%
Acid
Base
Neither
Both
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A solution with a [H+] =1x 10-5
has a pH of
10
1.
2.
3.
4.
0%
0%
0%
0%
1
5
9
14
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A solution with a pH of 8 has a
pOH of
10
1.
2.
3.
4.
0%
0%
0%
0%
2
6
8
14
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10
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A solution with a [OH-]=1x10-3
has a [H+] =
10
1.
2.
3.
4.
0%
0%
0%
0%
3
11
1 x 1011
1 x 10-11
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10
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Neutralization Reactions
 Neutralization reactions occur when acids react
with bases and produce a salt and water.
 A salt is an ionic compound consisting of the
positive ion of the base and the negative ion of
the acid.
 Example: HCl + NaOH  NaCl + H2O
acid
base
salt
water
 If the [H+] = [OH-], the resulting solution will
be neutral (pH=7).
 Neutralization reactions are a specific type of
double displacement reaction.
What salt is formed?





HCl + KOH 
H3PO4 + NaOH 
Ca(OH)2 + H2SO4 
Mg(OH)2 + HF 
HNO3 + NaOH 
Titration
 A titration is a method for
determining the concentration of a
solution by reacting a known volume
of that solution with a solution of
known concentration.
 The reaction that takes place is a
neutralization reaction.
Procedure for carrying out
titrations.
 A measured volume of
an acid or base is added
to a beaker or flask.
 A buret is filled with a
solution of known
concentration (titrant).
 The solution of known
concentration is added
until the solution in the
beaker has been
completely neutralized.
 This point is called the
equivalence point.
Titrations Continued
 You will recognize the
equivalence point
because the indicator will
change colors at this
point.
 This is also referred to as
the end point of the
titration.
 The volume that is added
to reach this point is
used to calculate the
unknown molarity.
Example
 25.0 mL of HCl is titrated to the
endpoint with 50.0 mL of 2.0 M
NaOH. What is the molarity of the
HCl?
MxV=MxV
 X (25.0) = 2.0 (50.0)
 X= 4.0 M
 http://www.mhhe.com/physsci/chemi
stry/animations/chang_7e_esp/crm3s
5_5.swf
Pre-lab: Which is the most
effective antacid?
 What makes an antacid effective?
 How does the antacid affect the acid?
 How will you determine which antacid
is most effective at neutralizing the
stomach acid?