1 / 48

Models of Acids and Bases

Models of Acids and Bases. Arrhenius Concept : Acids produce H + in solution, bases produce OH  ion. Models of Acids and Bases (continued). Brønsted-Lowry : Acids are H + donors, bases are proton acceptors. HCl + H 2 O  Cl  + H 3 O + acid base.

malise
Download Presentation

Models of Acids and Bases

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Models of Acids and Bases • Arrhenius Concept: Acids produce H+ in solution, bases produce OH ion.

  2. Models of Acids and Bases (continued) • Brønsted-Lowry: Acids are H+ donors, bases are proton acceptors. • HCl + H2O  Cl + H3O+ • acid base

  3. Models of Acids and Bases (continued) • H3O+ • Hydronium ion • Also written as H+

  4. Conjugate Acid/Base Pairs • conjugate base: everything that remains of the acid molecule after a proton is lost. • conjugate acid: formed when the proton is transferred to the base.

  5. Conjugate Acid/Base Pairs (continued) • HA(aq) + H2O(l)  H3O+(aq) + A(aq) • acid1 base2 conj conj • acid 2 base 1

  6. Identify the conjugate base of: • HCN • HSO4- • HF • H2PO4-

  7. Identify the conjugate acid of: • NH3 • HCO3- • Br-

  8. Identify the products of the reactions and label conj. Acids & bases • HNO3 + H2O  • HSO4- + H2O  • NH3 + H2O  • NH4++ H2O  • HCO3- + OH- 

  9. Acid Dissociation Constant (Ka) • HA(aq) + H2O(l)  H3O+(aq) + A(aq) • pKa = -log(Ka)

  10. Acid Strength Strong Acid: • Its equilibrium position lies far to the right. (HNO3) • Ka ≈∞ • Yields a weak conjugate base. (NO3)

  11. Strong Acids HCl, HBr, HI, HNO3, H2SO4, HClO4, HClO3

  12. Acid Strength(continued) Weak Acid: • Its equilibrium lies far to the left. (CH3COOH) • Yields a much stronger (it is relatively strong) conjugate base than water. (CH3COO)

  13. Bases • “Strong” and “weak” are used in the same sense for bases as for acids.

  14. Base Dissociation Constant (Kb) • B(aq) + H2O(l)  BH+(aq) + OH(aq) • pKb = -log(Kb)

  15. Bases (continued) • strong = complete dissociation (hydroxide ion supplied to solution) • Kb ≈∞ • NaOH(s)  Na+(aq) + OH(aq)

  16. Strong Bases Group I metal hydroxides Ca(OH)2, Ba(OH)2, Sr(OH)2

  17. Bases(continued) • weak = very little dissociation (or reaction with water) • H3CNH2(aq) + H2O(l)  H3CNH3+(aq) + OH(aq)

  18. Polyprotic Acids • . . . can furnish more than one proton (H+) to the solution.

  19. Water as an Acid and a Base • Water is amphoteric (it can behave either as an acid or a base).

  20. Water as an Acid and a Base (continued) H2O + H2O  H3O+ + OH • acid 1 base2conj conj • acid 2 base 1 • Kw =[H3O+][OH] =1  1014 at 25°C

  21. The pH Scale • pH log[H+] • pH in water ranges from 0 to 14. • pH<7 acidic • pH>7  basic • pH = 7  neutral

  22. The pH Scale (continued) • pKw = 14.00 = pH + pOH • As pH rises, pOH falls (sum = 14.00).

  23. Equation Summary • pH = -log[H3O+] • pOH = -log[OH-] • pH + pOH = 14 • [H3O+][OH-] = Kw = 1x10-14 Ka x Kb = Kw pKa = -log(Ka) pKb = -log(Kb)

  24. Fill in the blanks

  25. What is the pH of a 0.15M solution of HCl?

  26. What is the pH of a o.32M solution of Ba(OH)2?

  27. The pH of a solution of Ba(OH)2 is 10.66 at 25°C. If the solution volume is 125mL, how many grams of Ba(OH)2 must have been dissolved?

  28. What is the pH of a 0.15M solution of acetic acid?

  29. What is the pH of a 0.21M solution of ammonia?

  30. pH of a mixture • What is the pH of a mixture of 1.3M nitric acid and 1.5M acetic acid?

  31. What is the pH of a mixture of 1.00M HCN and 5.00M HNO2? What is [CN-] at equilibrium?

  32. pH of polyprotic acids • What is the pH of 2.0M H2SO4? • Ka1=∞, Ka2=1.2x10-2 • 2nd H+ isn’t significant

  33. What is the pH of 0.0010M H2SO4?At lower concentrations the 2nd H+ may be significant

  34. Percent Dissociation (Ionization) For weak acids, % dissociation increases as the acid/base becomes more dilute.

  35. %dissociation calculations • Calculate the % dissociation of 1.00M acetic acid.

  36. 0.100M HC3H5O2 has 3.7% dissociation. What is the Ka value?

  37. Acid-base properties of salts • “Salt” – generic term for an ionic compound • Cation is a conjugate acid • Anion is a conjugate base • NaCl Na+ conjugate acid of NaOH Cl- conjugate base of HCl

  38. Acid-Base Properties of Salts

  39. Acidic, Basic, or neutral? • NaNO3 • NaNO2 • NH4NO2 • KOCL • C5H5NHClO4 • NH4OCl

  40. pH of salt solutions • What is the pH of a 1.0M solution of sodium acetate?

  41. What is the pH of a 0.5M solution of ammonium chloride?

  42. Structure and Acid-Base Properties • The weaker the H+ is bonded to the molecule, the stronger the acid • Two factors for acidity in binary compounds: • Bond Polarity(high is good) • Bond Strength(low is good)

  43. Choose the strongest acid • HIO3 or HBrO3 • HNO2 or HNO3 • HOCl or HOI • H3PO4 or H3PO3

  44. Oxides • Acidic Oxides • Nonmetal oxides produce acidic solutions in water • (Acid Anhydrides): • OX bond is strong and covalent. • SO2, NO2, CrO3

  45. Oxides (continued) • Basic Oxides • Metal oxides produce basic solutions in water • (Basic Anhydrides): • OX bond is ionic. • K2O, CaO

  46. Lewis Acids and Bases • Lewis Acid: electron pair acceptor • Lewis Base: electron pair donor

  47. Identify the Lewis acids and bases

More Related