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pH Scale and Calculations

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

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pH Scale and Calculations

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  1. pH Scale and Calculations

  2. 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.

  3. pH Scale 7 Acid Base 0 14 Zumdahl, Zumdahl, DeCoste, World of Chemistry2002, page 515

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

  5. pH of Common Substance pH [H1+] [OH1-] pOH 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 100 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 7 1 x 10-7 1 x 10-7 7 More acidic

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

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

  8. Kw = [H3O+][OH-] • Kw - ion product of water Kw = 1.0 x 10-14 at 25 oC • This equilibrium constant is very important because it applies to all aqueous solutions - acids, bases, salts, and non-electrolytes

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

  10. pH and pOH • pH = - log[H3O+] [H3O+] = 10-pH pOH = - log[OH-] [OH-] = 10-pOH • pKw = pH + pOH = 14.00 • neutral solution: [H3O+] = [OH-] = 10 –7 M pH = 7.0 acidic solution: [H3O+] > 10-7 M pH < 7.0 basic solution: [H3O+] < 10-7 M pH > 7.0

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