Unit 14 – 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 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 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. Determining pH or [H3O+] Acidic or Basic Neutral

C. Determining 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+] = 0.01 M ? pH = - log (0.01) pH = 2.00 Acidic or Basic

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

Determining pOH pOH is a measure of the concentration of OH- ions pOH = -log[OH-] pH + pOH = 14 What is the pOH of a solution with a H+ concentration of 1 x 10-8? pH = -log(1 x 10-8) pOH = 14 - 8 pH = 8 pOH = 6

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

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 16

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 17

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 18

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+] 19