The pH Scale Hydronium & Hydroxide Ions (H3O+) (OH–) pH Scale Calculations Print 1-12
(in pure water) [H3O+] = [OH–] auto-ionization of water: H2O molecules ionize to H3O+ & OH– ions by proton (H+) transfer auto-ionization constant of water, Kw : Kw = [H3O+] x [OH–] = 1.0 x 10–14 (in pure water) [H3O+] = [OH–]
[H3O+] & [OH–] Acidic Neutral Basic = Kw = [H3O+] x [OH–]
pH Scale pH is… measure of acidity/basicity by concentration of H3O+ ions, or [H3O+] , or [H+] [H3O+] pH [H3O+] pH
pH Scale pure water (pH =7) WHY? pH is… measure of acidity/basicity by concentration of H3O+ ions, or [H3O+] , or [H+] pure water (pH =7) [H+] = [OH–], pure water WHY? Kw = [H3O+] x [OH–] = 1.0 x 10–14 (1 x 10–7 M) (1 x 10–7 M)
Average pH of: Blood -> 7.35 Coca Cola -> 2.35 Coffee -> 5 Seawater -> was 8.2 now is 8.1
Calculations pH = –log [H+] pOH = –log [OH–] [H+] = 10–pH [OH–] = 10–pOH Kw = [H+] x [OH–] = 1 x 10–14 (auto-ionization constant of water) pH + pOH = 14
Calculating pH or [H3O+] Acidic or Basic Neutral
Calculating pH or [H3O+] What is the pH of a solution with a H+ concentration of 1.0 x 10–12 M ? pH = – log (1.0 x 10–12) pH = 12.00 Acidic or Basic
Calculating pH or [H3O+] What is the pH of a solution with a [H+] = 0.045 M ? pH = – log (0.045) pH = 1.3 Acidic or Basic
Neutral [H+] pH pOH [OH–] Kw = [H+]x[OH–] 1 x 10–14 1 x 10–14 0.0 14.0 1 x 10–14 1 x 10–1 1.0 13.0 1 x 10–13 1 x 10–2 2.0 12.0 1 x 10–12 1 x 10–3 3.0 11.0 1 x 10–11 1 x 10–4 4.0 10.0 1 x 10–10 1 x 10–5 5.0 9.0 1 x 10–9 1 x 10–6 6.0 8.0 1 x 10–8 1 x 10–7 7.0 Kw = [H+]x[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 Neutral 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
Neutral [H+] pH pOH [OH–] Kw = [H+]x[OH–] 1 x 10–14 1 x 10–14 0.0 14.0 1 x 10–14 1 x 10–1 1.0 13.0 1 x 10–13 1 x 10–2 2.0 12.0 1 x 10–12 1 x 10–3 3.0 11.0 1 x 10–11 1 x 10–4 4.0 10.0 1 x 10–10 1 x 10–5 5.0 9.0 1 x 10–9 1 x 10–6 6.0 8.0 1 x 10–8 1 x 10–7 7.0 Kw = [H+]x[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 Neutral 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
Neutral [H+] pH pOH [OH–] Kw = [H+]x[OH–] 1 x 10–14 1 x 10–14 0.0 14.0 1 x 10–14 1 x 10–1 1.0 13.0 1 x 10–13 1 x 10–2 2.0 12.0 1 x 10–12 1 x 10–3 3.0 11.0 1 x 10–11 1 x 10–4 4.0 10.0 1 x 10–10 1 x 10–5 5.0 9.0 1 x 10–9 1 x 10–6 6.0 8.0 1 x 10–8 1 x 10–7 7.0 Kw = [H+]x[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 Neutral 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
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 14
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 15
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 16
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+] 17