Содержание
- 2. Vocabulary Acidity, alkalinity, aqueous Donor, acceptor Dissociation Indicator
- 3. Learning Objectives
- 4. Acids and Bases Arrhenius definition: Classified in terms of formula and behaviour in water Acid: Base:
- 5. Acids and Bases Brønsted-Lowry definition: An acid-base reaction is a proton transfer process Acid: Base: Proton
- 6. Brønsted-Lowry Acid-Bases Conjugate acid-base pairs: Every acid-base reaction has two conjugate acid-base pairs. NH4+ is the
- 7. Proton-Transfer using a Weak Base:
- 8. Proton-Transfer using a Weak Acid:
- 9. pH pH is defined as the negative base-10 logarithm of the hydronium ion concentration. pH =
- 10. Autoionization of Water As we have seen, water is amphoteric. In pure water, a few molecules
- 11. Ion-Product Constant The equilibrium expression for this process is Kc = [H3O+] [OH−] This special equilibrium
- 12. pH In pure water, Kw = [H3O+] [OH−] = 1.0 × 10−14 Because in pure water
- 13. pH Therefore, in pure water, pH = −log (1.0 × 10−7) = 7.00 An acid has
- 14. Some common pH values:
- 15. Other “p” Scales The “p” in pH tells us to take the negative log of the
- 16. Because [H3O+] [OH−] = Kw = 1.0 × 10−14, we know that −log [H3O+] + −log
- 17. How Do We Measure pH? For less accurate measurements, one can use Litmus paper “Red” paper
- 18. How Do We Measure pH? For more accurate measurements, one uses a pH meter, which measures
- 19. How much is the equilibrium displaced towards the formation of the products (ionization) What is the
- 20. Strong Acids You will recall that the six strong acids are HCl, HBr, HI, HNO3, H2SO4
- 21. Strong Bases Strong bases are the soluble hydroxides, which are the alkali metal and heavier alkaline
- 22. Example problem 1: What is the pH of a 7.52 x 10-4 M CsOH solution? Is
- 23. Example problem 2: What is the [H3O+] and [OH-] of a solution with a pH of
- 24. Dissociation Constants For a generalized acid dissociation, the equilibrium expression would be This equilibrium constant is
- 25. Dissociation Constants For a generalized base dissociation, the equilibrium expression would be This equilibrium constant is
- 26. For the example equation: CH3COOH ⇌ CH3COO- + H+ CH3COOH is the acid and CH3COO- is
- 27. Dissociation Constants The greater the value of Ka, the stronger the acid.
- 28. Calculating Ka from the pH The pH of a 0.10 M solution of formic acid, HCOOH,
- 29. Calculating Ka from the pH The pH of a 0.10 M solution of formic acid, HCOOH,
- 30. Calculating Ka from the pH pH = −log [H3O+] 2.38 = −log [H3O+] −2.38 = log
- 31. Calculating Ka from pH = 1.8 × 10−4
- 32. Calculating pH from Ka Calculate the pH of a 0.30 M solution of acetic acid, HC2H3O2,
- 33. Calculating pH from Ka The equilibrium constant expression is
- 34. Calculating pH from Ka Now,x = [H3O+] = [C2H3O2−] (1.8 × 10−5) (0.30) = x2 5.4
- 35. Calculating pH from Ka pH = −log [H3O+] pH = −log (2.3 × 10−3) pH =
- 36. Titration A known concentration of base (or acid) is slowly added to a solution of acid
- 37. Titration A pH meter or indicators are used to determine when the solution has reached the
- 38. acid alkali end-point METHYL ORANGE
- 39. acid alkali end-point acid alkali PHENOLPHTHALEIN
- 40. Acid-Base Indicators indicate the equivalence point of a titration. are weak organic acids for which weak
- 41. Acid-Base Indicators The sharp change in color of the indicator signals the end point of the
- 42. Indicator Colors and Ranges
- 43. Titration of a Strong Base with a Strong Acid The pH at the equivalence point in
- 44. Strong acid – Strong base © www.chemsheets.co.uk A2 1104 23-December-2016
- 45. Strong acid – Strong base © www.chemsheets.co.uk A2 1104 23-December-2016
- 46. Strong acid – Strong base © www.chemsheets.co.uk A2 1104 23-December-2016
- 47. Titration of a Weak Base with a Strong Acid The pH at the equivalence point in
- 48. Strong acid – Weak base © www.chemsheets.co.uk A2 1104 23-December-2016
- 49. Strong acid – Weak base © www.chemsheets.co.uk A2 1104 23-December-2016
- 50. Strong acid – Weak base © www.chemsheets.co.uk A2 1104 23-December-2016
- 51. Titration of a Weak Acid with a Strong Base The pH at the equivalence point in
- 52. Weak acid – Strong base © www.chemsheets.co.uk A2 1104 23-December-2016
- 53. Weak acid – Strong base © www.chemsheets.co.uk A2 1104 23-December-2016
- 54. Weak acid – Strong base © www.chemsheets.co.uk A2 1104 23-December-2016
- 55. Weak acid – Weak base pH at equivalence depends on relative strength of acid and base
- 56. Weak acid – Weak base © www.chemsheets.co.uk A2 1104 23-December-2016
- 57. Weak acid – Weak base © www.chemsheets.co.uk A2 1104 23-December-2016
- 58. SUMMARY © www.chemsheets.co.uk A2 1104 23-December-2016
- 59. SUMMARY © www.chemsheets.co.uk A2 1104 23-December-2016
- 60. SUMMARY © www.chemsheets.co.uk A2 1104 23-December-2016
- 61. Buffers: Solutions of a weak conjugate acid-base pair. They are particularly resistant to pH changes, even
- 62. Buffers If a small amount of hydroxide is added to an equimolar solution of HF in
- 63. Buffers If acid is added, the F− reacts to form HF and water.
- 64. Buffer Calculations Consider the equilibrium constant expression for the dissociation of a generic acid, HA:
- 65. Buffer Calculations Rearranging slightly, this becomes Taking the negative log of both side, we get
- 66. Buffer Calculations So Rearranging, this becomes This is the Henderson–Hasselbalch equation.
- 67. Henderson–Hasselbalch Equation What is the pH of a buffer that is 0.12 M in lactic acid,
- 68. Henderson–Hasselbalch Equation pH = 3.85 + (−0.08) pH = 3.77
- 69. Buffer Uses Electroplating Manufacture of Dyes Calibrating pH meters Buffering blood using combinations of: HCO3- ;
- 70. When Strong Acids or Bases Are Added to a Buffer… …it is safe to assume that
- 71. Addition of Strong Acid or Base to a Buffer Determine how the neutralization reaction affects the
- 72. Calculating pH Changes in Buffers A buffer is made by adding 0.300 mol HC2H3O2 and 0.300
- 73. Calculating pH Changes in Buffers The 0.020 mol NaOH will react with 0.020 mol of the
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