Transcript Document

Acids
Lesson 3
Strong and Weak
Bases
Strong and Weak Bases
Strong bases completely ionize in water to produce OH-.
There are 9 Arrhenius strong bases. They are Group I and heavy
(bottom 3) Group II hydroxides.
LiOH

Li+
+
OHNaOH

Na+ +
OHKOH

K+
+
OHRbOH

Rb+ +
OHCsOH

Cs+
+
OHFrOH

Fr+
+
OHSr(OH)2

Sr2+ +
2OHBa(OH)2

Ba2+ +
2OHRa(OH)2

Ra2+ +
2OHHighlight the nine metals on your periodic table
Note all bases make OH-
There are two more Bronsted type strong bases. They are found on the
right highlighted area of the acid chart -p 6.
O2NH2-
There are two more Bronsted type strong bases. They are found on the
right highlighted area of the acid chart -p 6.
O2NH2-
+
H2O
There are two more Bronsted type strong bases. They are found on the
right highlighted area of the acid chart -p 6.
O2-
NH2-
H+
+
H2O

There are two more Bronsted type strong bases. They are found on the
right highlighted area of the acid chart -p 6.
O2-
H+
+
NH2- +
H2O
H2O

OH-
+
OH-
There are two more Bronsted type strong bases. They are found on the
right highlighted area of the acid chart -p 6.
O2-
H+
+
H2O

H2O

H+
NH2- +
OH-
+
OH-
There are two more Bronsted type strong bases. They are found on the
right highlighted area of the acid chart -p 6.
O2-
H+
+
H2O

OH-
+
OH-
H2O

NH3
+
OH-
H+
NH2- +
There are two more Bronsted type strong bases. They are found on the
right highlighted area of the acid chart -p 6.
O2-
H+
+
H2O

OH-
+
OH-
H2O

NH3
+
OH-
H+
NH2- +
Again, all bases make OH-
Weak Bases
A weak base is one that partially reacts with water to produce OH-.
Arrhenius:
Zn(OH)2(s)
⇄
Zn2+
+
2OH-
Mg(OH)2(s)
⇄
Mg2+ +
2OH-
Be(OH)2(s)
⇄
Be2+
2OH-
+
These are the metal hydroxides that are not highlighted on the
periodic table.
The equilibrium is described by a Ksp
Ksp
=
[Zn2+][OH-]2
Bronsted Weak Bases:
F-
Bronsted Weak Bases:
F-
+
H2O
Bronsted Weak Bases:
H+
F-
+
H2O
Bronsted Weak Bases:
H+
F-
+
H2O
C2O42-
+
H2O
⇄
HF
+
OH-
Bronsted Weak Bases:
H+
F-
+
H2O
⇄
+
H2O
⇄
H+
C2O42-
HF
+
OH-
Bronsted Weak Bases:
H+
+
H2O
⇄
HF
+
OH-
C2O42-
+
H2O
⇄
HC2O4-
+
OH-
HCO3-
+
H 2O
FH+
Bronsted Weak Bases:
H+
F-
+
H2O
⇄
HF
+
OH-
+
H2O
⇄
HC2O4-
+
OH-
+
H 2O
⇄
H+
C2O42H+
HCO3-
Bronsted Weak Bases:
H+
+
H2O
⇄
HF
+
OH-
+
H2O
⇄
HC2O4-
+
OH-
HCO3-
+
H 2O
⇄
H2CO3
+
OH-
C6H5O73-
+
H2O
⇄
FH+
C2O42H+
Bronsted Weak Bases:
H+
+
H2O
⇄
HF
+
OH-
+
H2O
⇄
HC2O4-
+
OH-
HCO3-
+
H 2O
⇄
H2CO3
+
OH-
C6H5O73-
+
H2O
⇄
HC6H5O72-
+
OH-
NH3
+
H2O
⇄
FH+
C2O42H+
Bronsted Weak Bases:
H+
+
H2O
⇄
HF
+
OH-
+
H2O
⇄
HC2O4-
+
OH-
HCO3-
+
H 2O
⇄
H2CO3
+
OH-
C6H5O73-
+
H2O
⇄
HC6H5O72-
+
OH-
NH3
+
H2O
⇄
NH4+
+
OH-
FH+
C2O42H+
Bronsted Weak Bases:
H+
+
H2O
⇄
HF
+
OH-
+
H2O
⇄
HC2O4-
+
OH-
HCO3-
+
H 2O
⇄
H2CO3
+
OH-
C6H5O73-
+
H2O
⇄
HC6H5O72-
+
OH-
NH3
+
H2O
⇄
NH4+
+
OH-
FH+
C2O42H+
They all make OH- by accepting a proton from water!
Write the Kb expression for each weak base
Write the Kb expression for each weak base
Kb
=
[HF][OH-]
[F-]
Write the Kb expression for each weak base
Kb
=
[HF][OH-]
[F-]
Kb
=
[HC2O4-][OH-]
[C2O42-]
Write the Kb expression for each weak base
Kb
=
[HF][OH-]
[F-]
Kb
=
[HC2O4-][OH-]
[C2O42-]
Kb
=
[H2CO3][OH-]
[HCO3-]
Write the Kb expression for each weak base
Kb
=
[HF][OH-]
[F-]
Kb
=
[HC2O4-][OH-]
[C2O42-]
Kb
=
[H2CO3][OH-]
[HCO3-]
Kb
=
[HC6H5O72-][OH-]
[C6H5O73-]