Modern Chemistry Chapter 15
Acid-Base Titration & pH
Section 1
• self-ionization of water occurs when two
water molecules produce a hydronium
(H3O+) and a hydroxide (OH-) ion
2 H2O  H3O+ + OH-
• The ionization constant (Kw) of water is:
Kw = [H3O+] [OH-] = 1.0 x 10-14 M
Acidic, Basic, & Neutral
• IF [H3O+] > [OH-] then solution is acidic.
• IF [H3O+] < [OH-] then solution is basic.
• IF [H3O+] = [OH-] then solution is neutral.
Calculating [H3O+] & [OH-]
• Since the product of the hydronium and
hydroxide ion concentrations is a constant,
we can use the following formula to
determine these concentrations.
[H3O+] [OH-] = 1.0 x 10-14 M
Use this formula to answer problems #1-4
on page 502 of the textbook.
The pH Scale
• The pH of a solution is defined as the
negative of the common logarithm of the
hydronium ion concentration, [H3O+].
pH = -log [H3O+]
• The pOH of a solution is defined as the
negative of the common logarithm of the
hydroxide ion concentration, [OH-].
pOH = -log [OH-]
pH & pOH
pH + pOH = 14
14 – pH = pOH
14 – pOH = pH
so
and
See figure 3 on page on page 503.
See table 3 on page 504.
See table 4 on page 504.
Do problem #1 on page 505.
Do problems #1-4 on page 506.
Do problems #1-4 on page 508.
Cross-Disciplinary Connection
• Read the Cross-Disciplinary Connection titled
“Liming Streams” on page 510.
• Answer both questions at the end of the article.
Section 2
Determining pH and Titrations
• acid-base indicators are compounds
whose colors are sensitive to pH
• transition interval is the pH range over
which an indicator changes color
• a pH meter determines the pH of a
solution by measuring the voltage between
two electrodes placed in a solution.
Titration
• titration is the controlled addition and measurement of
the amount of a solution of a known concentration
required to react completely with a measured amount of
solution of an unknown concentration
• equivalence point is the point at which the two solutions
used in a titration are present in chemically equivalent
amounts
• endpoint is the point in a titration at which the indicator
changes color
• standard solution is the solution that contains a
precisely known concentration of solute
Titration
• see figure 10 on pages 518-519 for the
steps of a titration
• A general equation for the solution of
titration problems would be
VaMaeqa = VbMbeqb
Va = volume of acid
Ma = molarity of acid
eqa = #H in formula of acid
Vb = volume of base
Mb = molarity of base
eqb = #OH in formula of base
Titration
• Do practice problems #1-2 on page 521.
• Do section review problems #1-2 on page
521.
• Do chapter review problems #6, 8, 9, 12,
13, 24, 25, & 26 on pages 523-524.
Modern Chemistry Chapter 15
Test Review
• 25 multiple choice
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definition of self-ionization
[H3O+] [OH-] = 1 x 10-14
definition and formula for calculating pH = -log[H3O+]
pH >7 is a base; pH <7 is an acid; pH = 7 is neutral
pH range is normally 0 to 14
calculate pH from [H3O+]
calculate [H3O+] from pH
definitions of indicators, transition interval, titration,
neutralization, endpoint, standard solution
– acid-base titration monitors pH
– titration problems using VaMaeqa = VbMbeqb