Unit 13 – Acid, Bases, & Salts The pH Scale Hydronium & Hydroxide Ions (H3O+) (OH–) pH Scale Calculations Print 1-12

A. Hydronium & Hydroxide Ions H3O+ & OH– Ions auto-ionization of H2O by proton (H+) transfer

Kw – Ionization Constant for Water A. Hydronium & Hydroxide Ions Kw – Ionization Constant for Water In pure water at 25 C: [OH-] = [H3O+] = 1 x 10-7 M Kw is a constant at 25 C: Kw = [H3O+][OH-] Kw = (1 x 10-7)(1 x 10-7) = 1 x 10-14 [H3O+][OH-] = 1 x 10-14

A. Hydronium & Hydroxide Ions [H3O+][OH-] = 1 x 10-14 1. If [H3O+] is 1 x 10-9, what is [OH-]? (1 x 10-9) [OH-] = 1 x 10-14 [OH-] = 1 x 10-14 = 1 x 10-9 1 x 10-5 M

A. Hydronium & Hydroxide Ions [H3O+][OH-] = 1 x 10-14 2. If [H3O+] is 4.5 x 10-5, what is [OH-]? (4.5 x 10-5) [OH-] = 1 x 10-14 [OH-] = 1 x 10-14 = 4.5 x 10-5 2.2 x 10-10 M

A. Hydronium & Hydroxyl Ions Acidic more [H3O+] than [OH-] Basic more [OH–] than [H3O+]

B. pH Scale pH a measure of the concentration of H3O+ ions in solution, or [H3O+] [H+] same as [H3O+]

B. pH Scale pH a measure of the concentration of H3O+ ions in solution, or [H3O+] [H+] same as [H3O+] pH [H3O+] pH [H3O+]

pH of Common Substances B. pH Scale pH of Common Substances acidic pH < 7 Neutral basic pH > 7 WHY? pure water pH =7 [H+] = [OH–]

C. Calculations pH = –log [H+] pOH = –log [OH–] [H+] = 10–pH [OH–] = 10–pOH pH + pOH = 14 Kw = [H+] x [OH–] = 1 x 10–14 (auto-ionization constant of water)

C. Calculating pH or [H3O+] Acidic or Basic Neutral

C. Calculating pH or [H3O+] What is the pH of a solution with a H+ concentration of 1.0 x 10-10? pH = - log (1.0 x 10-10) pH = 10 Acidic or Basic

C. Calculating pH or [H3O+] What is the pH of a solution with a [H+] = 0.045 M ? pH = - log (0.045) pH = 1.35 Acidic or Basic

C. Calculating pH or [H3O+] What is the pH of a solution with a [H+] = 6.35 x 10-6 M ? pH = - log (6.35 x 10-6) pH = 5.20 Acidic or Basic

C. Calculating pOH pOH is a measure of the concentration of OH- ions in solution pOH = -log[OH-] and pH + pOH = 14 What is the pOH of a solution with a OH- concentration of 5.0 x 10-2? What is the pH of the above solution? pOH = -log(5.0 x 10-2) = 1.30 pH = 14.00 – 1.30 = 12.70

C. Calculating [H+] and [OH-] [H+] = 10-pH and [OH-] = 10-pOH 1. Calculate the concentration of H+ of a solution of with a pH of 2.50. [H+] = 10-2.50 = 3.16 x 10-3 M 2. Calculate [OH-] of a solution with a pH = 9.32. [OH-] = 10-4.68 = 2.09 x 10-5 M

Kw = [H+][OH–] 1 x 10–14 1 x 10–14 1 x 10–14 1 x 10–14 1 x 10–14 1 x 10–14 1 x 10–14 1 x 10–14 1 x 10–14 1 x 10–14 1 x 10–14 1 x 10–14 1 x 10–14 1 x 10–14 1 x 10–14

OH– H+ pH pOH C. Calculations [OH–] = 1 x 10–14 [H+] [H+] = 1 x 10–14 pH = –log[H+] [OH–] = 10–pOH pOH = –log[OH–] pOH = 14 – pH pH pOH pH = 14 – pOH

Quick Quiz! 1) Which one of the following solutions is the most basic? A) soap B) milk C) vinegar D) ammonia E) tomato juice F) blood pH ≈ 10 pH ≈ 6.5 pH ≈ 2.5 pH ≈ 11 pH ≈ 4.0 pH ≈ 7.4 20

Quick Quiz 2) The [H3O+] for four solutions is given below. Which one of the solutions is the most acidic? A) 1 x 10-3M B) 1 x 10-7M C) 1 x 10-9M D) 1 x 10-14M 21

Quick Quiz. 3) What is the pH of a solution with a [H+] concentration of 2.50 x 10-11M ? A) 12.93 B) 10.60 C) 8.92 D) 5.50 22

Quick Quiz. 4) What is the pH of a solution with a [OH–] concentration of 1.50 x 10-3M ? A) 2.82 B) 11.18 C) 6.67 x 10–12 D) 1.50 x 10–12 pOH = –log[OH–] pH = 14 – pOH OR [H+] = 1 x 10–14 [OH–] pH = –log[H+] 23