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II. pH (p. 644 – 658)

Ch. 19 – Acids & Bases. II. pH (p. 644 – 658). A. Ionization of Water. H 2 O + H 2 O H 3 O + + OH -. Self-Ionization of Water. A. Ionization of Water. K w = [H 3 O + ][OH - ] = 1.0  10 -14. Ion Product Constant for Water. The ion production of water, K w = [H 3 O + ][OH – ]

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II. pH (p. 644 – 658)

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  1. Ch. 19 – Acids & Bases II. pH(p. 644 – 658)

  2. A. Ionization of Water H2O + H2O H3O+ + OH- Self-Ionization of Water

  3. A. Ionization of Water Kw = [H3O+][OH-] = 1.0  10-14 Ion Product Constant for Water • The ion production of water, Kw = [H3O+][OH–] • Pure water contains equal concentrations of H+ and OH– ions, so [H3O+] = [OH–] • For all aqueous solutions, the product of the hydrogen-ion concentration and the hydroxide-ion concentration equals 1.0 x 10-14

  4. A. Ionization of Water Find the hydroxide ion concentration of 3.0  10-2 M HCl. HCl → H+ + Cl- 3.0  10-2M 3.0  10-2M [H3O+][OH-] = 1.0  10-14 [3.0  10-2][OH-] = 1.0  10-14 [OH-] = 3.3  10-13 M

  5. A. Ionization of Water Find the hydronium ion concentration of 1.4  10-3 M Ca(OH)2. Ca(OH)2→ Ca2+ + 2 OH- 1.4  10-3M 2.8  10-3M [H3O+][OH-] = 1.0  10-14 [H3O+][2.8  10-3] = 1.0  10-14 [H3O+] = 3.6  10-12 M

  6. B. pH Scale pouvoir hydrogène (Fr.) “hydrogen power” 14 0 7 INCREASING BASICITY INCREASING ACIDITY NEUTRAL pH = -log[H3O+]

  7. B. pH Scale pH of Common Substances

  8. B. pH Scale pH = -log[H3O+] pOH = -log[OH-] pH + pOH = 14

  9. B. pH Scale What is the pH of 0.050 M HNO3? pH = -log[H3O+] pH = -log[0.050] pH = 1.30 Acidic or basic? Acidic

  10. B. pH Scale What is the pH of 0.050 M Ba(OH)2? [OH-] = 0.100 M pOH = -log[OH-] pOH = -log[0.100] pOH = 1.00 pH = 13.00 Acidic or basic? Basic

  11. B. pH Scale What is the molarity of HBr in a solution that has a pOH of 9.60? pH + pOH = 14 pH + 9.60 = 14 pH = 4.40 pH = -log[H3O+] 4.40 = -log[H3O+] -4.40 = log[H3O+] [H3O+] = 4.0  10-5 M HBr Acidic

  12. C. pH Worksheet #6 A swimming pool has a volume of one million liters. How many grams of HCl would need to be added to that swimming pool to bring the pH down from 7.0000 to 4.0000? (Assume the volume of the HCl is negligible) 7 = -log[H+] -7 = log[H+] [H+] = 1 x 10-7 M 1,000,000L Sol’n 1x10-7 mol H+ 1 L soln = 0.1 mol H+ 1,000,000L Sol’n 1x10-4 mol H+ 1 L soln -4 = log[H+] [H+] = 1 x 10-4 M = 100 mol H+

  13. C. pH Worksheet #6 A swimming pool has a volume of one million liters. How many grams of HCl would need to be added to that swimming pool to bring the pH down from 7.0000 to 4.0000? (Assume the volume of the HCl is negligible) 100 mol H+ – 0.1 mol H+ = 99.9 mol HCl 99.9 mol HCl = 3642 g HCl 36.46 g HCl 1 mol HCl

  14. D. pH Sig Figs • For the pH, the number of sig figs is shown by the # of decimal places • [H+] = 2.26 x 10-4 M => • For the molarity from the pH, check decimal places in the pH • pH = 4.25 => pH = 3.646 5.6 x 10-5 M

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