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Chapter 16

Chapter 16. Acids and Bases. Characteristics. Acids: Bases: Change the color of dyes. Characteristics. Add acid to water makes water Add base to water makes it more Add acid to base NaOH + HCl  NaCl + H 2 O. Acids. Bases. Arrhenius. Acids. Bases. Bronsted/Lowry.

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Chapter 16

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  1. Chapter 16 Acids and Bases

  2. Characteristics • Acids: • Bases: • Change the color of dyes

  3. Characteristics • Add acid to water makes water • Add base to water makes it more • Add acid to base • NaOH + HCl  NaCl + H2O

  4. Acids Bases Arrhenius

  5. Acids Bases Bronsted/Lowry

  6. Water as a Bronsted/Lowry • H2O  H+ + OH- • H+ + H2O H3O+ • Hydronium can bond to many other water molecules

  7. Water and Hydronium • H2O + HCl  H3O+ + Cl-

  8. Ammonia as a base • HCl +NH3 NH4 + Cl- • H2O +NH3  NH4 + OH- • An acid and a base always work together to transfer protons.

  9. Amphoteric Species • A compound that can • Water • Base with HCl • Acid with NH3

  10. Conjugate acids and bases • Every acid/base reaction has • H2O +NH3  NH4 + OH-

  11. Practice • What are the conjugate bases of the following acids?

  12. Practice • What are the conjugate acids of the following bases?

  13. Strong Acids • 100% ionized • Reaction is not reversible

  14. Strong Bases • 100% ionized • CH3- is a VERY strong base • No acidity and takes proton from water

  15. Weak Acids • Slightly dissociated • CH3COOH + H2O  CH3COO- + H3O+ • Scale on page 598, fig 16.4

  16. Generally • HX + H2O  H3O+ + X- • Equilibrium favors transfer of proton from stronger acid to stronger base

  17. Practice • NH4+ + OH- NH3 + H2O • Does the equilibrium lie to the right or left? • Why

  18. Autoionization of water • H2O+ H2O  H3O+ + OH- • This is a very fast reaction • Only about 1 out of 109 water molecules are dissociated at any time

  19. Generally • Shown as: • H2O  H+ + OH-

  20. Ion Product • H2O(l) + H2O(l) H3O+(aq) + OH-(aq) • Kc = • But water is a constant so…

  21. MEMORIZE THIS! • Kc • Kw = • At equilibrium

  22. Practice • Remember: at equilibrium • Identify the following as acid or base • [H+] = 1 e –5 • [OH-] = 3.2 e –9 • [H+] = 7.1 e –8 • [OH-] = 4.6 e –3

  23. pH scale • Pain to always use exponents • Use logarithmic scale to deal with exponent • MEMORIZE:

  24. So… • If • Therefore… the pH of a neutral solution is 7 • (equal amounts of H+ and OH-)

  25. Calculations involving pH • If given [OH-] there are two methods to get pH • 1.

  26. Calculations involving pH • What is pH if [OH-] = 3.2 e-5? • 2.

  27. The pH scale • If the pH < 7, the solution is acidic • If the pH > 7, the solution is basic • If the pH = 7, the solution is neutral • See fig 16.5 p. 602

  28. Practice • Calculate the pH of lemon juice that has a

  29. How do you undo a logarithm? • If • Then

  30. Practice • What is the [H+] of a solution that has a pH of • What is the [OH-] of each solution?

  31. Practice • What is the pH of • What is the pH of • What is [HNO3] is

  32. Quiz • What is the pH of a solution that has [OH-] = • What is the [H+] of a solution that has a • What is the pOH of a solution that has a • Identify all of the above as either acid/base

  33. Weak Acids… • Write the acid ionization expression for HCHO2, formic acid, dissolving in water. This is an equilibrium expression. • This gets the designation

  34. HCHO2 H+ + CHO2- • A student prepared a 0.10 M solution of formic acid and measured its pH. At 25oC, it was found to be 2.38. • Calculate Ka • ICE BOX!!!

  35. Niacin… • A 0.20 M solution of niacin has a pH of 3.26. what is the Ka for niacin? • ICE BOX!!!!

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