Chapter 15
Acid and Bases
This is the first of two chapters dealing with acids and bases. Upon completion of this
chapter, your students should be able to:
1.
Compare and contrast Arrhenius, Brønsted, and Lewis acids and bases.
2.
Describe what is meant by conjugate acidbase pairs and give several examples.
3.
Use K
w
to determine [H
+
] and [OH

] of solutions.
4.
Define the pH scale and calculate pH and pOH given either [H
+
] or [OH

].
5.
Define strong and weak acids and bases; give several examples of each.
6.
List properties of conjugate acidbase pairs.
7.
Determine K
a
from experimental data.
8.
Calculate pH, [H
+
], weak acid concentration, and conjugate base concentration given K
a
and the initial concentration of the weak acid using the quadratic equation or the method
of successive approximation as needed.
9.
Calculate percent ionization for a weak acid.
10. Calculate pH, [OH

], weak base concentration, and conjugate acid concentration given K
b
and the initial concentration of the weak base, using the quadratic equation or the method
of successive approximation as needed.
11. Illustrate the relationship between K
a
, K
b
, and K
w
.
12. Calculate concentrations of all species present at equilibrium for diprotic and polyprotic
acids.
13. Relate how molecular structure determines the strength of acids.
14. Compare the relative strengths of two groups of oxoacids.
15. Describe salt hydrolysis and explain how some salts produce neutral solutions, some
acidic solutions, and others basic solutions.
16. Calculate the pH of salt solutions and determine the percent hydrolysis.
17. Describe acidbase properties of oxides and hydroxides.
18. Give several examples of Lewis acidbase reactions.
Section 15.1
Brønsted Acids and Bases
Brønsted acid is defined as a chemical species that is capable of donating a proton while a
Brønsted base accepts a proton. For each Brønsted acid there is a corresponding conjugate
base. For each Brønsted base there is a corresponding conjugate acid. It is important to note
that a Brønsted acid/base conjugate pair differ in that the acid has an additional H
+
compared
to
that of the corresponding base. It should be noted that water can be either a
Brønsted acid or base depending on what else is in solution. Water is also said to be
amphoteric or amphiprotic.
Section 15.2
The AcidBase Properties of Water
The autoionization of water can be written as
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View Full DocumentSince this is an equilibriumexpression, the equilibrium constant can be written as
However, since the concentration of water (approximately 55 M) does not significantly
change by the very small amount of water that autoionizes, this constant value can be
incorporated in Kc to give a new constant we call
w
. K
w
, like all equilibrium constants, is
temperature dependent; however, at 25
0
C it has a value of 1.0 Η 10
14
. Therefore,
Kw=[H
+
][OH

]=1.0 ×10
14
It should be noted that even in the most concentrated acid solution [OH

] always has a
nonzero value. (It can never equal zero because then the product of [H
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 Spring '10
 Shaklovich
 pH, Weak acid, H+

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