# pH Scale and Calculations Chapter 14 Page 565-574.

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pH Scale and Calculations Chapter 14 Page 565-574

pH Scale We use this scale to measure the strength of an acid or base. pH is defined as the –log[H+] pH can use the concentration of hydronium ions or hydrogen ions.

pH Scale Acid Base 0 7 14 Zumdahl, Zumdahl, DeCoste, World of Chemistry  2002, page 515

pH of Common Substances Timberlake, Chemistry 7 th Edition, page 335

pH of Common Substance 14 1 x 10 -14 1 x 10 -0 0 13 1 x 10 -13 1 x 10 -1 1 12 1 x 10 -12 1 x 10 -2 2 11 1 x 10 -11 1 x 10 -3 3 10 1 x 10 -10 1 x 10 -4 4 9 1 x 10 -9 1 x 10 -5 5 8 1 x 10 -8 1 x 10 -6 6 6 1 x 10 -6 1 x 10 -8 8 5 1 x 10 -5 1 x 10 -9 9 4 1 x 10 -4 1 x 10 -10 10 3 1 x 10 -3 1 x 10 -11 11 2 1 x 10 -2 1 x 10 -12 12 1 1 x 10 -1 1 x 10 -13 13 0 1 x 10 0 1 x 10 -14 14 NaOH, 0.1 M Household bleach Household ammonia Lime water Milk of magnesia Borax Baking soda Egg white, seawater Human blood, tears Milk Saliva Rain Black coffee Banana Tomatoes Wine Cola, vinegar Lemon juice Gastric juice More basic More acidic pH [H 1+ ] [OH 1- ] pOH 7 1 x 10 -7 1 x 10 -7 7

Acid – Base Concentrations pH = 3 pH = 7 pH = 11 OH - H3O+H3O+ H3O+H3O+ H3O+H3O+ [H 3 O + ] = [OH - ] [H 3 O + ] > [OH - ] [H 3 O + ] < [OH - ] acidic solution neutral solution basic solution concentration (moles/L) 10 -14 10 -7 10 -1 Timberlake, Chemistry 7 th Edition, page 332

pH pH = -log [H + ] Kelter, Carr, Scott, Chemistry A World of Choices 1999, page 285

Self-Ionization Of Water Even the purest of water conducts electricity. This is due to the fact that water self-ionizes, that is, it creates a small amount of H 3 O + and OH -. H 2 O + H 2 O º H 3 O + + OH - K w =[H 3 O + ][OH - ] K w - ion product of water K w = 1.0 x 10 -14 at 25 o C This equilibrium constant is very important because it applies to all aqueous solutions - acids, bases, salts, and non-electrolytes - not just to pure water.

O H H O H H O Self ionization reaction of water: + O H H H H + + -

pH and pOH pH = - log[H 3 O + ][H 3 O + ] = 10 -pH pOH = - log[OH - ][OH - ] = 10 -pOH pK w = pH + pOH = 14.00 neutral solution: [H 3 O + ] = [OH - ] = 10 –7 M pH = 7.0 acidic solution: [H 3 O + ] > 10 -7 M pH < 7.0 basic solution: [H 3 O + ] 7.0

Practice Finish the following for homework Page 566 #12-15 (using Kw) Page 569 # 16-19 (using pH = -log[H+] Page 572 # 20-23 Page 578 # 2, 6-8