1.
Nils Walter: Chem 260
weak base + strong acid
Acid-base titrations quantitatively
HClO(aq) + OH-(aq) ClO-(aq) + H2O(aq)
]
[
]
[
3
3
acid
a
base
a
a
a
K
O
H
HClO
O
H
ClO
a
+
+
− ×
≈
×
=
⇒
⇒
⇒
⇒
]
[
]
[
3
base
acid
K
a a
O
H
×
≈
+ ⇒
⇒
⇒
⇒
]
[
]
[
log
base
acid
pK
pH a −
≈
Henderson-Hasselbalch equation
Determination of
the pKa of an acid
a
pK
pH ≈
]
[
]
[
base
acid
=

2.
Nils Walter: Chem 260
Buffers and indicators
acid buffer: stabilizes pH @
below pH 7 (around pKa)
In
pK
pH
base
acid
−
=
]
[
]
[
log
Indicators:

3.
Nils Walter: Chem 260
Solubility equilibria
Ca(OH)2(s) Ca2+(aq) + 2 OH-(aq)
2
2 −
+ ×
= OH
Ca
s a
a
K
solubility constant
molar solubility ]
[
2
1
]
[ 2 −
+
=
= OH
Ca
S
3
2
4
)
2
( S
S
S
Ks =
×
=
⇒
⇒
⇒
⇒ 3
1
)
4
1
( s
K
S ≈
⇒
⇒
⇒
⇒
(ignoring
ion-ion interactions;
a ≈
≈
≈
≈ [ ])
AgCl(s) Ag+(aq) + Cl-(aq)
2
10
10
6
.
1
]
][
[ M
Cl
Ag
a
a
K Cl
Ag
s
−
−
+
×
=
≈
×
= −
+
]
[
]
[ −
+
≈
=
Cl
K
Ag
S s
AgCl can be precipitated by
addition of Cl- as a common
ion from, e.g., NaCl (Le
Chatelier!)

4.
Nils Walter: Chem 260
Chemistry involving ions: Electrochemistry
Atkins, Chapter 9
Ions migrate in electric fields
-
+
+ -
⇓
⇓
⇓
⇓
a current flows
I
V
R =
resistance ]
[Ω
=
A
l
ρ
potential difference
current
resistivity
length of sample
cross-sectional area
]
[
1 1
1
1 −
−
−
=
Ω
= Sm
m
ρ
κ
conductivity
siemens
]
[ 1
2 −
=
Λ mol
Sm
c
m
κ
molar conductivity:

5.
Nils Walter: Chem 260
Ionic conductivities
The molar conductivity varies with concentration
(ions influence each other)
c
K
o
m
m −
Λ
=
Λ
For a strong electrolyte (complete dissociation) [Kohlrausch (1876)]:
−
+ +
=
Λ λ
λ
o
m
Limiting molar conductivity (c →
→
→
→ 0 M)
ionic conductivities = contributions
of cation and anion species
Constant to take ion-ion
interactions into account