Drill: A M solution of HZ ionizes 20.0 %. Calculate: K aHZ

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 pK a

pK a or pK b pK a = - log K a pK b = - log K b

Buffer Equilibria

Buffer Problems Calculate the pH of a solution containing 0.10 M HAc in 0.10 M NaAc: K a = 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 NH 3 in 0.20 M NH 4 NO 3 : K b = 1.8 x 10 -5

Buffer Problems Calculate the pH of a solution containing 0.10 M HBz in 0.20 M NaBz: K a = 6.4 x 10 -5

Drill: Calculate the pH of a solution containing 0.30 M HZ in 0.10 M NaZ: K a = 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 Problem Calculate the pH of a solution containing 0.50 M R-NH 2 in 0.10 M R-NH 3 I: K b = 4.0 x 10 -5

HAH + + A - [ H + ][ A - ] [ HA ] K a =

HAH + + A - [ K a ][ HA ] [ A - ] [H + ]=

HAH + + A - [ HA ] [ A - ] [H + ] = (K a )

pH = [ HA ] [ A - ] pK a - log

Henderson- Hasselbach Eq [A - ] [HA] pH = pK a + log

Henderson- Hasselbach Eq [B + ] [B] pOH = pK b + log

Buffer Problems Calculate the salt to acid ratio to make a buffer solution with pH = 5.0 K a for HBZ = 2.0 x 10 -5

Equivalence Point Point at which the # of moles of the two titrants are equal

Titration Curves

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 K b 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

Calculate the HCO 3 - to H 2 CO 3 ratio in blood with pH = 7.40 K a1 for H2CO3 = 4.4 x 10 -7

150 ml of 0.10 M NaOH is added to ml of 0.10 M H 2 CO 3. Calculate pH. K a1 for H2CO3 = 4.4 x K a2 for H2CO3 = 4.8 x

AP CHM HW Read: Chapter 14 Problem: 33 Page: 422

CHM II HW Read: Chapter 19 Problem: 31 Page: 819