L37S09_Polyprotic+Acids,+Amino+Acids+04-24-09

L37S09_Polyprotic Ac - Chem 1A L 37"Polyprotic Acids Amino Acids" Summary TITRATION WEAK-ACID BASE ©A.Pines,M.Kubinec,UCB L36-1

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Unformatted text preview: Chem 1A L 37: "Polyprotic Acids, Amino Acids " Summary TITRATION WEAK-ACID BASE ©A.Pines,M.Kubinec,UCB L36-1 ChemQuiz© 36.2 Shown in yellow is the titration of HNO3 per mole KOH. Which is KOH. the correct curve for x10 dilution of HNO3? A) ©A.Pines,M.Kubinec,UCB H2O HNO3 B) mol OHmol OH- C) mol OHL36-2 ChemQuiz© 36.2 Solution moles HNO3 unchanged: equivalence point unchanged 10 x diliution = 1 pH unit 10 x diliution = 1 pH unit mol OH- 1) ©A.Pines,M.Kubinec,UCB 2) mol OHmol OH- 3) mol OHL36-3 ©A.Pines,M.Kubinec,UCB 1 Chem 1A L 37: "Polyprotic Acids, Amino Acids " ChemQuiz© 36.3 Shown is in yellow the titration of HAc per mole KOH. Which is the KOH. correct curve for x10 dilution of HAc? HAc? A) ©A.Pines,M.Kubinec,UCB H2O HAc B) mol OHmol OH- C) mol OHL36-4 ChemQuiz© 36.3 Solution moles HAc unchanged: equivalence point unchanged 10 x diliution < 1 pH unit mol OH- Buffer region unchanged A) ©A.Pines,M.Kubinec,UCB B) mol OHmol OH- C) mol OHL37-5 Summary ©A.Pines,M.Kubinec,UCB L37-6 ©A.Pines,M.Kubinec,UCB 2 Chem 1A L 37: "Polyprotic Acids, Amino Acids " PolyProtic Acids: Indicators Thymol Blue (H2Thy) (H Thy) TheypH pKa2 Thy-2 + H+ pKa2 = 8.8 pKa1 H2Thy HThy- + H+ +OH- pKa1 = 2.0 2.0 ©A.Pines,M.Kubinec,UCB L37-7 PolyProtic Acids H2CO3 pH H3PO4 H2SO4 trend: pKa1 < pKa2 < pKa3 pKa2 pKa1 HCO3H2CO3 +OH- CO3-2 + H3O+ pKa2 = 10.25 HCO3- + H3O+ pKa1 = 6.37 6.37 ©A.Pines,M.Kubinec,UCB L37-8 ChemQuiz 37.1 Which carbonate species is present in the highest concentration at pH 7 ? pKa2 pKa1 1) H2CO3 ©A.Pines,M.Kubinec,UCB 2) HCO3 -1 3) CO3 -2 L37-9 ©A.Pines,M.Kubinec,UCB 3 Chem 1A L 37: "Polyprotic Acids, Amino Acids " PolyProtic Acids/Blood Buffer Blood pH Stats: pH PCO = 40 torr 2 pKa2 pKa1 +OH©A.Pines,M.Kubinec,UCB [CO2] = 1.2 mM [CO2] = [H2CO3] Carbonic Anhydrase Kidneys Lungs Henry’s Law Henry’ [HCO3-] = 24 mM L37-11 PolyProtic Acids/Blood Buffer Blood pH Stats: [HCO3-] log PCO = 40 torr 2 pH = pKa* + 6.1 [H2CO3] [CO2] = 1.2 mM [1.2] 1.2] [CO2] = [H2CO3] [H Carbonic Anhydrase pH = 7.40 ± 0.05 [HCO3-] = 24 mM Kidneys L37-12 [24] 24] Lungs Henry’s Law Henry’ *at body temperature ©A.Pines,M.Kubinec,UCB 9.0 Amino Acid pKa’s C C C C +N -O OC C + N 9.1 pH = 7.0 10.5 10.1 C C C C C C O 2.2 Lysine O +N 2.2 C C C - O Tyrosine ©A.Pines,M.Kubinec,UCB L37-13 ©A.Pines,M.Kubinec,UCB 4 Chem 1A L 37: "Polyprotic Acids, Amino Acids " Amino Acid pKa’s + 2.0 O 10 N C C O C 3.9 O 9.2 N N C C C C pH = 7.0 C O - Aspartic Acid O O + C N N C C C N N 6.0 C C ©A.Pines,M.Kubinec,UCB 1.8 O O Histidine L37-14 ChemQuiz© 37.2 pKa= 9.0 What is the total effective charge on the amino acid cysteine at pH 5.0 ? N + C O C C S pKa= 8.0 pKa= 2.2 Cysteine A) + 1 ©A.Pines,M.Kubinec,UCB B) 0 C) -1 L37-15 Lecture complete ©A.Pines,M.Kubinec,UCB L37-17 ©A.Pines,M.Kubinec,UCB 5 ...
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This note was uploaded on 04/24/2010 for the course CHEM 1A taught by Professor Nitsche during the Spring '08 term at University of California, Berkeley.

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