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Chapters 13-14

Chapters 13-14. Acids, Bases, Buffers. Common Acids. HCl HNO 3 H 2 SO 4 H 3 PO 4 H 4 SiO 4 HBr H I H 2 SO 3 Patterns?. Common Acids. HCl HNO 3 H 2 SO 4 H 3 PO 4 H 4 SiO 4 HBr H I H 2 SO 3 Patterns? All contain H.

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Chapters 13-14

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  1. Chapters 13-14 • Acids, Bases, Buffers

  2. Common Acids • HCl • HNO3 • H2SO4 • H3PO4 • H4SiO4 • HBr • HI • H2SO3 • Patterns?

  3. Common Acids • HCl • HNO3 • H2SO4 • H3PO4 • H4SiO4 • HBr • HI • H2SO3 Patterns? • All contain H. • H was written first.

  4. Common Bases • NaOH • LiOH • KOH • Ca(OH)3 • Ba(OH)2 • Mg(OH)2 • Al(OH)3 • Si(OH)4 • NH4OH Patterns?

  5. Common Bases • NaOH • LiOH • KOH • Ca(OH)3 • Ba(OH)2 • Mg(OH)2 • Al(OH)3 • Si(OH)4 • NH4OH Patterns? • all contain OH, written second.

  6. Definitions • Arrhenius - (common)(specific) • Acid - releases contained H+ ions • Base - releases contained OH- ions • Bronsted - Lowry • Acid - proton (H+) donor • Base - proton (H+) acceptor • Lewis (general) • Acid - accepts an electron pair • Base - donates an electron pair

  7. Conjugate Acid-Base Pairs(B-L) • HB(aq) + A-(aq) HA (aq) + B -(aq)

  8. Conjugate Acid-Base Pairs(B-L) • D A D A • Who donates, who accepts • conjugate acid base pairs • pair 1 D A Pair 2 D A • HB(aq) + A-(aq) HA (aq) + B -(aq)

  9. Conjugate Acid-Base Pairs(B-L) • D A D A • Who donates, who accepts • conjugate acid base pairs • pair 1 D A Pair 2 D A • HB(aq) + A-(aq) HA (aq) + B -(aq)

  10. Conjugate Acid-Base Pairs(B-L) • D A D A • Who donates, who accepts • conjugate acid base pairs • pair 1 DA Pair 2 A D • HB(aq) + A-(aq) HA (aq) + B -(aq)

  11. Special Case • H2O(l) + H2O(l) H3O+(aq) + OH -(aq) • autoionization of water • OR • H2O(l) + H2O(l) H+(aq) + OH -(aq) • If the thought of naked protons running around in a pool does not bother you, • This is simpler!

  12. Special Case • H2O(l) + H2O(l) H3O+(aq) + OH -(aq) • autoionization of water • OR • H2O(l) + H2O(l) H+(aq) + OH -(aq) • If the thought of naked protons running around in a pool does not bother you, • This is simpler!

  13. Special Case • H2O(l) + H2O(l) H3O+(aq) + OH -(aq) • autoionization of water • OR • H2O(l) + H2O(l) H+(aq) + OH -(aq) • If the thought of naked protons running around in a pool does not bother you, • This is simpler!

  14. Special Case • H2O(l) + H2O(l) H3O+(aq) + OH -(aq) • autoionization of water • OR • H2O(l) + H2O(l) H+(aq) + OH -(aq) • If the thought of naked protons running around in a pool does not bother you, • this is simpler!

  15. K #3 • H2O(l) + H2O(l) H+(aq) + OH -(aq) • Keq(water) = Kw = [H+(aq)][OH-(aq)] = 1 x 10-14 • Why is the water not included??? • [H+(aq)] = [OH-(aq)] means water is neutral. • [H+(aq)][OH-(aq)] = 1 x 10-14 • ∴ [H+(aq)]2 = 1 x 10-14 Why? • ∴ [H+(aq)]= 1 x 10-7 neutralWhy?

  16. the power of Hydrogen ions • [H+(aq)]= 1 x 10-7 neutralstronger weaker • [H+(aq)]= 1 x 10-6 acid base? • [H+(aq)]= 1 x 10-5 acid base? • [H+(aq)]= 1 x 10-4 acid base? • [H+(aq)]= 1 x 10-3 acid base? • [H+(aq)]= 1 x 10-2 acid base? • [H+(aq)]= 1 x 10-1 acid base? • [H+(aq)]= 1 x 100 acid base?weaker stronger • ? ?

  17. the power of Hydrogen ions • [H+(aq)]= 1 x 10-7 neutralstronger weaker • [H+(aq)]= 1 x 10-6 acid base? • [H+(aq)]= 1 x 10-5 acid base? • [H+(aq)]= 1 x 10-4 acid base? • [H+(aq)]= 1 x 10-3 acid base? • [H+(aq)]= 1 x 10-2 acid base? • [H+(aq)]= 1 x 10-1 acid base? • [H+(aq)]= 1 x 100 acid base?weaker stronger • ? ?

  18. the power of Hydrogen ions • [H+(aq)]= 1 x 10-7 = .0000001weaker • [H+(aq)]= 1 x 10-6 = .000001 • [H+(aq)]= 1 x 10-5 = .00001 • [H+(aq)]= 1 x 10-4 = .0001 • [H+(aq)]= 1 x 10-3 = .001 • [H+(aq)]= 1 x 10-2 = .01 • [H+(aq)]= 1 x 10-1 = .1 • [H+(aq)]= 1 x 100 =1. we aker stronger • ? ?

  19. the power of Hydrogen ions • pH • [H+(aq)]= 1 x 10-7 = .00000017weaker • [H+(aq)]= 1 x 10-6 = .000001 6 • [H+(aq)]= 1 x 10-5 = .00001 5 • [H+(aq)]= 1 x 10-4 = .0001 4 • [H+(aq)]= 1 x 10-3 = .001 3 • [H+(aq)]= 1 x 10-2 = .01 2 • [H+(aq)]= 1 x 10-1 = .1 1 • [H+(aq)]= 1 x 100 =1. 0 stronger • ? ?

  20. the power of Hydrogen ions • pH • [H+(aq)]= 1 x 10-7 = .00000017weaker • [H+(aq)]= 1 x 10-6 = .000001 6 • [H+(aq)]= 1 x 10-5 = .00001 5 • [H+(aq)]= 1 x 10-4 = .0001 4 • [H+(aq)]= 1 x 10-3 = .001 3 • [H+(aq)]= 1 x 10-2 = .01 2 • [H+(aq)]= 1 x 10-1 = .1 1 • [H+(aq)]= 1 x 100 =1. 0 stronger • ? ?

  21. the power of Hydrogen ions • pH • [H+(aq)]= 1 x 10-7 = .00000017weaker • [H+(aq)]= 1 x 10-6 = .000001 6 • [H+(aq)]= 1 x 10-5 = .00001 5 • [H+(aq)]= 1 x 10-4 = .0001 4 • [H+(aq)]= 1 x 10-3 = .001 3 • [H+(aq)]= 1 x 10-2 = .01 2 • [H+(aq)]= 1 x 10-1 = .1 1 • [H+(aq)]= 1 x 100 =1. 0 stronger • ? ?

  22. the power of Hydrogen ions • pH • [H+(aq)]= 1 x 10-7 = .00000017weaker • [H+(aq)]= 1 x 10-6 = .000001 6 • [H+(aq)]= 1 x 10-5 = .00001 5 • [H+(aq)]= 1 x 10-4 = .0001 4 • [H+(aq)]= 1 x 10-3 = .001 3 • [H+(aq)]= 1 x 10-2 = .01 2 • [H+(aq)]= 1 x 10-1 = .1 1 • [H+(aq)]= 1 x 100 =1. 0 stronger • ? ?

  23. the power of Hydrogen ions • pH • [H+(aq)]= 1 x 10-7 = .00000017weaker • [H+(aq)]= 1 x 10-6 = .000001 6 • [H+(aq)]= 1 x 10-5 = .00001 5 • [H+(aq)]= 1 x 10-4 = .0001 4 • [H+(aq)]= 1 x 10-3 = .001 3 • [H+(aq)]= 1 x 10-2 = .01 2 • [H+(aq)]= 1 x 10-1 = .1 1 • [H+(aq)]= 1 x 100 =1. 0 stronger • ? ?

  24. the power of Hydrogen ions • pH • [H+(aq)]= 1 x 10-7 = .00000017weaker • [H+(aq)]= 1 x 10-6 = .000001 6 • [H+(aq)]= 1 x 10-5 = .00001 5 • [H+(aq)]= 1 x 10-4 = .0001 4 • [H+(aq)]= 1 x 10-3 = .001 3 • [H+(aq)]= 1 x 10-2 = .01 2 • [H+(aq)]= 1 x 10-1 = .1 1 • [H+(aq)]= 1 x 100 =1. 0 stronger • ? ?

  25. the power of Hydrogen ions • pH • [H+(aq)]= 1 x 10-7 = .00000017weaker • [H+(aq)]= 1 x 10-6 = .000001 6 • [H+(aq)]= 1 x 10-5 = .00001 5 • [H+(aq)]= 1 x 10-4 = .0001 4 • [H+(aq)]= 1 x 10-3 = .001 3 • [H+(aq)]= 1 x 10-2 = .01 2 • [H+(aq)]= 1 x 10-1 = .1 1 • [H+(aq)]= 1 x 100 =1. 0 stronger • ? ?

  26. the power of Hydrogen ions • pH • [H+(aq)]= 1 x 10-7 = .00000017weaker • [H+(aq)]= 1 x 10-6 = .000001 6 • [H+(aq)]= 1 x 10-5 = .00001 5 • [H+(aq)]= 1 x 10-4 = .0001 4 • [H+(aq)]= 1 x 10-3 = .001 3 • [H+(aq)]= 1 x 10-2 = .01 2 • [H+(aq)]= 1 x 10-1 = .1 1 • [H+(aq)]= 1 x 100 =1. 0 stronger • ? ?

  27. Definitions and Other Stuff • pH = - log[H+] • pOH = - log[OH-] • As pH gets larger, acid content drops • As pOH gets larger, base content drops • pH + pOH = 14 • [H+][OH-] = 1 x 10-14

  28. Acid-Base Differences • Strong Acids • Weak acids • Strong Bases • Weak bases

  29. Strong Acids (6 only) • HCl HBr HI • HNO3 H2SO4 HClO4 • HCl(aq)H+(aq) + Cl-(aq) • So little product returns, reaction considered 100% ionized

  30. Weak acids • a) ionizable H+ • HB(aq) + H2O(l) B-(aq) + H3O+(aq) • OR • HB(aq)B-(aq) + H+(aq) • So little H+ ionizes, most of the acid molecule remains intact. • b) cations • B+(aq) + H2O(l) BOH(aq) + H+(aq) • Certain anions have the ability to promote H+ ionization. • So little product returns, reaction considered 100% ionized

  31. K #4 • Weak acids • HB(aq) + H2O(l) B-(aq) + H3O+(aq) • HB(aq)B-(aq) + H+(aq) • weak acid ionization constant • Ka = [H+][B-] =[H3O+][B-] • [HB] [HB] • pKa = -log Ka • So little product returns, reaction considered 100% ionized

  32. Polyprotic Acids • Example: H3PO4 • H3PO4(aq) H2PO4-(aq) + H+(aq) • H2PO4-(aq) HPO4-2(aq) + H+(aq) • HPO4 -2(aq) PO4-3(aq) + H+(aq) • K1=[H2PO4-][H +]K2=[HPO4 -2][H +]K3=[PO4 -3][H +] • [H3PO4][H2PO4-] [HPO4 -2]

  33. Polyprotic Acids • Complex Equilibria • H3PO4(aq) H2PO4-(aq)HPO4-2(aq)PO4-3(aq) • + + + • H+(aq) H+(aq) H+(aq)

  34. Strong Bases (6 only) • LiOH NaOH KOH • Ca(OH)2 Sr(OH)2 Ba(OH)2 • LiOH(aq) Li+(aq) + OH-(aq) • So little product returns, reaction considered 100% ionized

  35. Weak bases • a) molecules • BH(aq) + H2O(l) BH2+(aq) + OH-(aq) • Certain molecules have the ability to promote OH- ions • b) anions • B-(aq) + H2O(l) BH(aq) + OH-(aq) • Certain anions have the ability to promote OH- ions • So little product returns, reaction considered 100% ionized

  36. K #5 • Weak bases • BH(aq) + H2O(l) BH2+(aq) + OH-(aq) • B-(aq) + H2O(l) BH(aq) + OH-(aq) • Kb = [BH+][OH-] =[BH][OH-] • [BH][B-] • pKb = -log Kb • So little product returns, reaction considered 100% ionized • weak base ionization constant

  37. Relationships • (Ka)(Ka) = 1 x 10-14 • pKa + pKa = 14

  38. Titration Possibilities • SASB • SAWB • WASB • WAWB

  39. SASB • Strong Acid • H+ • Strong Base • OH- • Strong Acid-Strong Base • Net Ionic Equation • H++ OH-H2O

  40. SAWB • Strong Acid • H++OH-H2O • Weak Base • BH +H2O BH2+ + OH- • B -+H2O BH+ OH- • Net Ionic Equation • BH +H+ BH2+ • B -+H+ BH

  41. WASB • Strong Base • H+ + OH- H2O • Weak Acid • HB B -+ H+ • Net Ionic Equation • HB +OH- B -+H2O

  42. WAWB • Weak Base • BH +H2O BH2+ + OH- • D -+H2O DH+ OH- • Weak Acid • HB B -+ H+ • Net Ionic Equation • BH + HBB -+ BH2+ • D -+HBB - + DH

  43. Buffers • Ability to resist change • meter out change

  44. Buffers • Contain:weak acids • conjugate bases • example: HF H++ F- • Ka = [H+][F-]= 3.50 x 10-4 • [HF] • [H+] = Ka [HF] • [F-]

  45. Buffers • suppose: [HF] = .1, [F-] = .1 • Ka= 3.50 x 10-4 • [H+] = 3.50 x 10-4[.1] • [.1] • pH = - log [H+] = 3.46

  46. Buffer Action • HF H+ + F- • F- + H2O HF + OH- • Add .01 moles OH- • HF H++ OH-+ F- • .1-.01= .09 .1+.01= .11 • H+ = 3.50 x 10-4(.09) • (.11) • pH = 3.50

  47. Buffer Action • HF H+ + F- • F- + H2O HF + OH- • Add .01 moles H+ • HF H++ H++ F- • .1+.01= .11 .1-.01= .09 • H+ = 3.50 x 10-4(.11) • (.09) • pH = 3.37

  48. Buffer Action • pH ranged from 3.37 to 3.50 in this buffer • Compare to: strong acid • [H+] = 1.85 x 10-5 pH = 4.74 • [H+] = 1.0 x 10-14 add .01 [OH-] • [OH-] • [H+] = 1.0 x 10-14= 1.0 x 10-12 • .01 pH = 12

  49. Summary of Buffer Action • Buffer / addition of .01 base • pH ranged 3.46 to 3.50 • No buffer / addition of .01 base • pH range 4.74 to 12

  50. Titration:SASB • 50.00 ml of 1 M HCl • titrate with 1 M NaOH • beginning pH = -log[1] = 0 • moles 1/1000 = x/50 = .05000

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