Drill: A 0.100 M solution of HZ ionizes 20.0 %. Calculate: K aHZ.
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Transcript of Drill: A 0.100 M solution of HZ ionizes 20.0 %. Calculate: K aHZ.
Drill: A 0.100 M solution of HZ ionizes 20.0 %.Calculate: KaHZ
DistributeMake-UpTitration
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
BufferEquilibria
Buffer Problems•Calculate the pH of a
solution containing
0.10 M HAc in 0.10 M NaAc: Ka = 1.8 x 10-5
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:
• Kb = 1.8 x 10-5
Buffer ProblemsCalculate the pH of a
solution containing
0.10 M HBz in 0.20 M NaBz: Ka = 6.4 x 10-5
Drill:Calculate the pH of a
solution containing
0.30 M HZ in 0.10 M NaZ: Ka = 3.0 x 10-5
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 ProblemCalculate the pH of a
solution containing
0.50 M R-NH2 in 0.10 M R-NH3I: Kb = 4.0 x 10-5
HA H+ + A-
[H+][A-]
[HA]Ka =
HA H+ + A-
[Ka][HA]
[A-][H+]=
HA H+ + A-
[HA]
[A-][H+] = (Ka)
pH =
[HA]
[A-]pKa - log
Henderson-Hasselbach Eq
[A-]
[HA]pH = pKa + log
Henderson-Hasselbach Eq
[B+]
[B]pOH = pKb+ log
Buffer Problems•Calculate the salt to acid
ratio to make a buffer solution with pH = 5.0
•Ka for HBZ = 2.0 x 10-5
Equivalence PointPoint at which the # of moles of the two
titrants are equal
Titration Curves
0
2
4
6
8
10
12
14
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 ProblemsCalculate the salt to base
ratio to make a buffer solution with pH = 9.48
• Kb for MOH = 2.0 x 10-5
Drill:Calculate the pH of a buffer solution containing 0.50 M HX in 0.25 M KX.
Ka = 2.5 x 10-5
Test
•Friday
0
2
4
6
8
10
12
14
0 20 40 60 80 100
[H2A] = [HA-]
[H2A] = [OH-]
[HA-] = [A-2]
[OH-] = [A-2]
Calculate the HCO3- to
H2CO3 ratio in blood with pH = 7.40
•Ka1 for H2CO3 = 4.4 x 10-7
150 ml of 0.10 M NaOH is added to 100.0 ml of 0.10 M H2CO3. Calculate pH.
• Ka1 for H2CO3 = 4.4 x 10-7
• Ka2 for H2CO3 = 4.8 x 10-11
AP CHM HW•Read: Chapter 14
•Problem: 33
•Page: 422
CHM II HW•Read: Chapter 19
•Problem: 31
•Page: 819