Drill: A 0.100 M
solution of HZ
ionizes 20.0 %.
Calculate: KaHZ
Distribute
Make-Up
Titration
Labs
Return
& Review
Tests
CHM II HW
• Review PP-23
• Complete the attached
assignment & turn it in
on Monday
Buffer
Solutions
Buffer Solution
•A solution that
resists changes in
pH
Buffer Solution
•Made from the
combination of a
weak acid & its
salt
Buffer Solution
•Made from the
combination of a
weak base & its
salt
Buffer Examples
•Mix acetic acid &
sodium acetate
•Mix ammonia &
ammonium chloride
Buffer Solution
•A buffer solution
works best when the
acid to salt ratio is
1:1
Buffer Solution
•A buffer solution
works best when the
base to salt ratio is
1:1
Buffer Solution
•The buffering capacity
of a solution works best
when the pH is near the
pKa
pKa or pKb
•pKa = - log Ka
•pKb = - log Kb
Buffer
Equilibria
Buffer Problems
•Calculate the pH of a
solution containing
0.10 M HAc in 0.10 M
-5
NaAc: Ka = 1.8 x 10
AP CHM HW
•Problem: 9
•Page: 421
CHM II HW
•Problem: 11
•Page: 818
Buffer Problems
•Calculate the pH of
0.10 M NH3 in
0.20 M NH4NO3:
-5
•Kb = 1.8 x 10
Buffer Problems
Calculate the pH of a
solution containing
0.10 M HBz in 0.20 M
-5
NaBz: Ka = 6.4 x 10
Drill:
Calculate the pH of a
solution containing
0.30 M HZ in 0.10 M
-5
NaZ: Ka = 3.0 x 10
Review Drill
&
Check HW
All who were
absent for the
Titration Lab need
to get a make-up
lab.
The Titration
Lab is due
Wednesday
Anyone who wants
to retake the last test
should see me to
make arrangements
to make it up.
Anyone who has
missed a previous
test should also see
me to make
arrangements to
make it up.
CHM II HW
• Review PP-23
• Complete the attached
assignment & turn it in
tomorrow.
Buffer Problem
Calculate the pH of a
solution containing
0.50 M R-NH2 in 0.10 M
-5
R-NH3I: Kb = 4.0 x 10
HA
+
H
+A
[ ][ ]
Ka =
[HA]
+
H
A
HA
+
H
+A
[
K
][
HA
]
a
+
[H ]=
[A ]
HA
+
H
+A
[
HA
]
+
[H ] = (Ka)
[A ]
pH =
[HA]
pKa - log
[A ]
HendersonHasselbach Eq
[A ]
pH = pKa + log [HA]
HendersonHasselbach Eq
+
[B ]
pOH = pKb+ log [B]
Buffer Problems
•Calculate the salt to acid
ratio to make a buffer
solution with pH = 5.0
-5
•Ka for HBZ = 2.0 x 10
Equivalence Point
Point at which the #
of moles of the two
titrants are equal
Titration
Curves
14
12
10
8
6
4
2
0
0.00
10.00
20.00
30.00
40.00
50.00
AP CHM HW
•Read: Chapter 14
•Problem: 23
•Page: 421
CHM II HW
•Read: Chapter 19
•Problem: 21
•Page: 819
Buffer Problems
Calculate the salt to base
ratio to make a buffer
solution with pH = 9.48
-5
•Kb for MOH = 2.0 x 10
Drill:
Calculate the pH of a
buffer solution
containing 0.50 M HX
in 0.25 M KX.
-5
Ka = 2.5 x 10
Test
•Friday
14
12
[OH-] = [A-2]
10
8 [HA-] = [A-2]
6
[H2A] = [OH-]
4
2
[H2A] = [HA-]
0
0
20
40
60
80
100
-
Calculate the HCO3 to
H2CO3 ratio in blood
with pH = 7.40
-7
•Ka1 for H2CO3 = 4.4 x 10
150 ml of 0.10 M NaOH
is added to 100.0 ml of
0.10 M H2CO3.
Calculate pH.
-7
•Ka1 for H2CO3 = 4.4 x 10
-11
•Ka2 for H2CO3 = 4.8 x 10
AP CHM HW
•Read: Chapter 14
•Problem: 33
•Page: 422
CHM II HW
•Read: Chapter 19
•Problem: 31
•Page: 819