Chapter 17 – Acids, Bases, and Salts
Section 17.1 – Brønsted Acids and Bases
What is a Brønsted acid? a substance that can donate a
proton
What is a Brønsted base? a substance that can accept a proton
What is a conjugate base of an acid? The anion that remains after a bronsted acid donates a proton
What is a conjugate acid of a base? The cation that results when a bronsted base accepts a
proton
In the following reaction, identify each reactant as a Brønsted acid or Brønsted base. Then,
>
loses
identify the conjugate acid-base pairs. a
proton
gains
a
proton
- -
H2SO4 (aq) + OH– (aq) → H2O (l) + HSO4– (aq)
acid base cacid c .
base
Work through Worked Example 17.1 and 17.2. Once you understand the steps needed to
solve this type of problem, challenge yourself with the 3 Practice Problems (Attempt, Build,
Conceptualize).
Q1: List the conjugate acids for each of the following:
H3Ot
H2O _____________ HzPOy
HPO42− ________________ HBr
Br- _________________
Q2: List the conjugate bases for each of the following:
OH-
H2O _____________ POp-
HPO4-2 ________________ CHsNH2
CH3NH3+ _________________
Section 17.2 – Molecular Structure and Acid Strength
The strength of an acid is measure by ____________________________________________.
it's ability to ionize
strength of the H-X bond
The two factors that influence the strength of an acid HX is (1) the _________
and (2) the __________
polarity of the H-X bond.
1. The stronger the H-X bond, the _________
weaker the acid.
2. The more polar the H-X bond, the __________
stronger the acid.
·
polarity & strength are directly related
·
bond strength & acid strength are inversely related
1
, What are hydrohalic acids? Halogens that form a series of binary acids (HF HC) HBr , and
, ,
HI)
The predominant factor in determining the strength of the hydrohalic acids is the
bond strength
____________.
List the hydrohalic acids in order of increasing acid strength:
H-F < H-CI < H-Br < H-I
weakest
strongest
What are oxoacids? What atom is the H+ bonded to in all oxoacids?
contain hydrogen oxygen and
, ,
a central nonmetal atom
0-H
Comparing oxoacid strength:
1. When comparing oxoacids with different central atoms that are from the same group of the
periodic table and that have the same oxidation number (i.e. same # of oxygen atoms): acid
strength increases with increasing _________________
electronegativity of the central atom.
CI is more electronegative than Br.
• HClO3 is a stronger acid than HBrO3 for this reason. Do you expect HIO3 to be weaker or
stronger than HBrO3? H10z will be a weaker acid than HBrOs because H10z has
less electronegative central atom (1) than HBrOs (Br) .
Br is more electronegative.
2. When comparing oxoacids with the same central atom but different numbers of oxygen
atoms: acid strength increases as the central atom’s oxidation number (# of oxygen atoms)
_______________.
increases
the stronger the acid .
The more oxygen atoms ,
Work through Worked Example 17.3. Once you understand the steps needed to solve this type
of problem, challenge yourself with the 3 Practice Problems (Attempt, Build, Conceptualize).
Predict the relative strengths of the oxoacids in each of the following groups :
(a) HCIO and HBrO and (b)
HNOz and HNOz
-
(a) HCIO is stronger than HBrO because they have the same oxidation I , so we look at the
electronegativities of the central atom.
Since CI is more electronegative than Br ,
HCIO is the stronger acid
(b) HNOz is stronger than HNO2 because it has the
higher oxidation #.
2
, Section 17.3 – The Acid-Base Properties of Water
What is an amphoteric substance?
An oxide that shows both acidic & basic acid base)
properties (can be both an or a
Complete the chemical equation below to show how two water molecules react. This is known
as the autoionization of water. Label the conjugate acid and the conjugate base.
Off- +
HzOT
c .
base c .
acid
Kw = [ Hz0t ] × [ ] = 1.0 x 10-14 at 25 °C
-
OH
Note that in ALL aqueous solutions, both H3O+ and OH– are present.
What is [H3O+] and [OH−] in pure water at 25°C?
if (H30 ] [OH-]
+
=
1 .
0x10-l CHgO ]
+
=
1 .
0x10" & [OH-] =
1 0
.
x 10
Work through Worked Example 17.4. Once you understand the steps needed to solve this type
of problem, challenge yourself with the 3 Practice Problems (Attempt, Build, Conceptualize).
Section 17.4 – The pH and pOH Scales
Describe how pH and pOH are defined and how the quantities are related.
log [H30 ] log [OH -] 14
+
pH = -
pOH = -
pH + pOH = _______ @ 25°C
Rewrite the equations for pH and pOH above to solve for [H3O+] or [OH−]:
I
1 0 x10-14
[H3O+] = [OH−] =
.
[H30 ]
+
Complete the table below to describe aqueous solutions.
Classification Relative ion concentration pH at 25 °C
Acidic [ItzO ]
+
> COH-] more acid pH < 7
Neutral [H3O+] = [OH–] pH =
7
Basic [HzO ]
+
< [OH] more base
pH > 7
3
Section 17.1 – Brønsted Acids and Bases
What is a Brønsted acid? a substance that can donate a
proton
What is a Brønsted base? a substance that can accept a proton
What is a conjugate base of an acid? The anion that remains after a bronsted acid donates a proton
What is a conjugate acid of a base? The cation that results when a bronsted base accepts a
proton
In the following reaction, identify each reactant as a Brønsted acid or Brønsted base. Then,
>
loses
identify the conjugate acid-base pairs. a
proton
gains
a
proton
- -
H2SO4 (aq) + OH– (aq) → H2O (l) + HSO4– (aq)
acid base cacid c .
base
Work through Worked Example 17.1 and 17.2. Once you understand the steps needed to
solve this type of problem, challenge yourself with the 3 Practice Problems (Attempt, Build,
Conceptualize).
Q1: List the conjugate acids for each of the following:
H3Ot
H2O _____________ HzPOy
HPO42− ________________ HBr
Br- _________________
Q2: List the conjugate bases for each of the following:
OH-
H2O _____________ POp-
HPO4-2 ________________ CHsNH2
CH3NH3+ _________________
Section 17.2 – Molecular Structure and Acid Strength
The strength of an acid is measure by ____________________________________________.
it's ability to ionize
strength of the H-X bond
The two factors that influence the strength of an acid HX is (1) the _________
and (2) the __________
polarity of the H-X bond.
1. The stronger the H-X bond, the _________
weaker the acid.
2. The more polar the H-X bond, the __________
stronger the acid.
·
polarity & strength are directly related
·
bond strength & acid strength are inversely related
1
, What are hydrohalic acids? Halogens that form a series of binary acids (HF HC) HBr , and
, ,
HI)
The predominant factor in determining the strength of the hydrohalic acids is the
bond strength
____________.
List the hydrohalic acids in order of increasing acid strength:
H-F < H-CI < H-Br < H-I
weakest
strongest
What are oxoacids? What atom is the H+ bonded to in all oxoacids?
contain hydrogen oxygen and
, ,
a central nonmetal atom
0-H
Comparing oxoacid strength:
1. When comparing oxoacids with different central atoms that are from the same group of the
periodic table and that have the same oxidation number (i.e. same # of oxygen atoms): acid
strength increases with increasing _________________
electronegativity of the central atom.
CI is more electronegative than Br.
• HClO3 is a stronger acid than HBrO3 for this reason. Do you expect HIO3 to be weaker or
stronger than HBrO3? H10z will be a weaker acid than HBrOs because H10z has
less electronegative central atom (1) than HBrOs (Br) .
Br is more electronegative.
2. When comparing oxoacids with the same central atom but different numbers of oxygen
atoms: acid strength increases as the central atom’s oxidation number (# of oxygen atoms)
_______________.
increases
the stronger the acid .
The more oxygen atoms ,
Work through Worked Example 17.3. Once you understand the steps needed to solve this type
of problem, challenge yourself with the 3 Practice Problems (Attempt, Build, Conceptualize).
Predict the relative strengths of the oxoacids in each of the following groups :
(a) HCIO and HBrO and (b)
HNOz and HNOz
-
(a) HCIO is stronger than HBrO because they have the same oxidation I , so we look at the
electronegativities of the central atom.
Since CI is more electronegative than Br ,
HCIO is the stronger acid
(b) HNOz is stronger than HNO2 because it has the
higher oxidation #.
2
, Section 17.3 – The Acid-Base Properties of Water
What is an amphoteric substance?
An oxide that shows both acidic & basic acid base)
properties (can be both an or a
Complete the chemical equation below to show how two water molecules react. This is known
as the autoionization of water. Label the conjugate acid and the conjugate base.
Off- +
HzOT
c .
base c .
acid
Kw = [ Hz0t ] × [ ] = 1.0 x 10-14 at 25 °C
-
OH
Note that in ALL aqueous solutions, both H3O+ and OH– are present.
What is [H3O+] and [OH−] in pure water at 25°C?
if (H30 ] [OH-]
+
=
1 .
0x10-l CHgO ]
+
=
1 .
0x10" & [OH-] =
1 0
.
x 10
Work through Worked Example 17.4. Once you understand the steps needed to solve this type
of problem, challenge yourself with the 3 Practice Problems (Attempt, Build, Conceptualize).
Section 17.4 – The pH and pOH Scales
Describe how pH and pOH are defined and how the quantities are related.
log [H30 ] log [OH -] 14
+
pH = -
pOH = -
pH + pOH = _______ @ 25°C
Rewrite the equations for pH and pOH above to solve for [H3O+] or [OH−]:
I
1 0 x10-14
[H3O+] = [OH−] =
.
[H30 ]
+
Complete the table below to describe aqueous solutions.
Classification Relative ion concentration pH at 25 °C
Acidic [ItzO ]
+
> COH-] more acid pH < 7
Neutral [H3O+] = [OH–] pH =
7
Basic [HzO ]
+
< [OH] more base
pH > 7
3
