L35S07_Weak Acid-Base-Titration 04-16-07

L35S07_Weak Acid-Base-Titration 04-16-07 - Chem 1A L 35:...

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Chem 1A L 35: "Weak Acid and Base, Titration" Weak Acid/Base (HAc/Ac-) (HAc/Ac acid Weak Base/Acid (NH3/NH4+) NH3 + H2O base acid base HAc + H2O Summary + - base acid H3O+ + Ac - Ka = 1.8x10-5 pKa = 4.7 base base OH- + NH4+ Kb = 1.8x10-5 pKb = 4.7 base acid - acid + acid H2O + Ac- base acid HAc + OH - Kb = 5.6x10-10 pKb = 9.3 L36-4 - H2O + NH4+ base acid NH3 + H3O+ Ka = 5.6x10-10 pKa = 9.3 L36-5 + A.Pines,M.Kubinec,UCB A.Pines,M.Kubinec,UCB Conjugate Acid/Base Pair HAc+H2O HAc+H Ka = + H3O ++Ac- + - H2O +Ac- HAc +OH- [H30 ][Ac ] [HAc] HAc] X [HAc][OH-] HAc][OH Kb = [Ac-] Ka Kb = [H30+][OH-] = Kw A.Pines,M.Kubinec,UCB L28-7 A.Pines,M.Kubinec,UCB L35-1 ChemQuiz 34.2 For the Acids HA1 and HA2, pKa1 < pKa2. Which is true for HA1 + 1) K < 1 A2HA2 + 2) K = 1 A13) K > 1 L35-2 HA1 HA2 A.Pines,M.Kubinec,UCB ChemQuiz 34.3 For the Acids HA1 and HA2, pKa1 < pKa2. Which is true for HA1 + A2HA2 + A1- HA1 HA2 1) K = Ka1+Ka2 A.Pines,M.Kubinec,UCB 2) K = Ka1Ka2 3) K =Ka1/Ka2 L35-4 A.Pines,M.Kubinec,UCB 1 Chem 1A L 35: "Weak Acid and Base, Titration" Weak Acid-Weak Base pH ~ 1 ~4 ~7 ~ 10 ~ 13 HCl 1 HAc 2 H2O 3 NH3 4 NaOH 5 L35-6 A.Pines,M.Kubinec,UCB ChemQuiz 35.1 If solutions 1 and 5 are mixed, what will be the: mixed, pH: 1) Acidic 1) A.Pines,M.Kubinec,UCB 2) Neutral 2) 3) Basic 3) L35-7 ChemQuiz 35.2 If solutions 2 and 4 are mixed, what will be the: mixed, pH: 1) Acidic 1) A.Pines,M.Kubinec,UCB 2) Neutral 2) 3) Basic 3) L35-9 A.Pines,M.Kubinec,UCB 2 Chem 1A L 35: "Weak Acid and Base, Titration" pH Titration of a Weak Acid by a Strong Base D C B AE.P. A HA Summary TITRATION O + Ac HAc + H O H WEAK-ACID BASE OH0.1 - x 2 Region A : 0.1 M HAc 3 + - x x Expect: 1.0 < pH < 7.0 HA/AHA/ Buffer acid HA + OH- base H2O + A- acid base Assume 0.1-x ? 0.1 0.1x2 = Ka = 1.76 x 10-5 0.1- x pH = 2.88 0.1x2 = 0.1 Ka x = 1.33x10-3 L29-6 + OHA.Pines,M.Kubinec,UCB L29-4 A.Pines,M.Kubinec,UCB Region C : 0.1 M AcAc - + H2O 0.1 - x HAc +OHx Expect: x 7.0 < pH < 13.0 Assume 0.1-x ? 0.1 0.1x2 = Kb = 5.68 x 10-10 0.1- x pH = 8.88 0.1x2 = 0.1 Kb A.Pines,M.Kubinec,UCB x = 7.5x10-6 L29-8 Titration of a Weak Acid by a Strong Base D pH pH C B A HA HA/AHA/ Buffer OH- AE.P. acid HA + OH- base H2O + A- acid base + OHA.Pines,M.Kubinec,UCB L35-13 Titration of a Weak Base by a Strong Acid pH pH B B/BH+ Buffer BH+ E.P. base B + H3O+ acid base H2O + BH+ acid H3O+ + H3O+ A.Pines,M.Kubinec,UCB L35-14 A.Pines,M.Kubinec,UCB 3 Chem 1A L 35: "Weak Acid and Base, Titration" Region A : 0.1 M HAc HAc + H2O 0.1 - x H3O++ Ac- 1.0 < pH < 7.0 x x + - Expect: Assume 0.1-x 0.1 0.1x2 = Ka = 1.76 x 10-5 0.1- x pH = 2.88 0.1x2 = 0.1 Ka A.Pines,M.Kubinec,UCB x = 1.33x10-3 L35-15 ChemQuiz 35.3 A solution of a) HCl b) HAc of pH = 3.0 is diluted x 10. 10. What is the new pH ? H2O HCl 1) < 4.0 A.Pines,M.Kubinec,UCB 2) = 4.0 3) > 4.0 L35-16 Region C : 0.1 M AcAc - + H2O HAc +OHx Expect: 7.0 < pH < 13.0 x - 0.1 - x x2 Assume 0.1-x 0.1 0.1= Kb = 5.68 x 10-10 x = 7.5x10-6 L35-19 0.1- x 0.1- pH = 8.88 x2 = 0.1 Kb A.Pines,M.Kubinec,UCB A.Pines,M.Kubinec,UCB 4 Chem 1A L 35: "Weak Acid and Base, Titration" ChemQuiz 35.4 Consider the titration of the following with a strong acid/base. For which is the pH at the equivalence point less than 7 ? A) HCl pKa ~ -7 2) HCOOH pKa ~ 3 3) NH3 pKb ~ 5 L35-20 A.Pines,M.Kubinec,UCB Lecture complete A.Pines,M.Kubinec,UCB L35-22 A.Pines,M.Kubinec,UCB 5 ...
View Full Document

Ask a homework question - tutors are online