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