Understanding pH Sources: 1. Anthony Carpi, Acids, Bases and pH, http://web.jjay.cuny.edu/~acarpi/NSC/7-ph.htm, 1998-1999 2. Paul Decelles, The pH Scale, http://staff.jccc.net/pdecell/chemistry/phscale.html, 6/20/2002

Water Molecule H2O

H2O H2O

Proton Exchange H2O HO- Hydroxide H2O H3O+ Hydronium

Proton Exchange HO- Hydroxide H2O H3O+ Hydronium H2O

High concentration of OH- Base Low concentration of H3O+

High concentration of H3O+ Acid Low concentration of OH-

[H3O+] Concentration in moles/liter [OH-] Concentration in moles/liter pH [OH-] Concentration in moles/liter Example 1  X 100 1  X 10-14 Battery acid, Strong HCl (4%) 1  X 10-1 1 1  X 10-13 Stomach acid 1  X 10-2 2 1  X 10-12 Lemon juice 1  X 10-3 3 1  X 10-11 Orange juice, Vinegar, Gastric juices 1  X 10-4 4 1  X 10-10 Acid rain, Tomato juice, Soda 1  X 10-5 5 1  X 10-9 Rainwater (unpolluted), Black coffee 1  X 10-6 6 1  X 10-8 Milk, Urine, Saliva 1  X 10-7 7 Pure water 8 Egg whites 9 Baking Soda 10 Tums® (antacid) 11 Ammonia 12 Mineral Lime 13 Bleach, Oven cleaner 14 Drano®, NaOH (4%) Acid Neutral Base

[H3O+] Concentration in moles/liter [OH-] Concentration in moles/liter pH [OH-] Concentration in moles/liter Example 1  X 100 1  X 10-14 Battery acid, Strong HCl (4%) 1  X 10-1 1 1  X 10-13 Stomach acid 1  X 10-2 2 1  X 10-12 Lemon juice 1  X 10-3 3 1  X 10-11 Orange juice, Vinegar, Gastric juices 1  X 10-4 4 1  X 10-10 Acid rain, Tomato juice, Soda 1  X 10-5 5 1  X 10-9 Rainwater (unpolluted), Black coffee 1  X 10-6 6 1  X 10-8 Milk, Urine, Saliva 1  X 10-7 7 Pure water 8 Egg whites 9 Baking Soda 10 Tums® (antacid) 11 Ammonia 12 Mineral Lime 13 Bleach, Oven cleaner 14 Drano®, NaOH (4%) What is pH? pH is the opposite of the log of the concentration of Hydronium ions measured in moles per liter or pH = - log (concentration H3O+ ) - log (1 x 10-3 ) = 3 Examples - log (1 x 10-7 ) = 7 - log (1 x 10-11 ) = 11

[H3O+] Concentration in moles/liter [OH-] Concentration in moles/liter pH [OH-] Concentration in moles/liter Example 1  X 100 1  X 10-14 Battery acid, Strong HCl (4%) 1  X 10-1 1 1  X 10-13 Stomach acid 1  X 10-2 2 1  X 10-12 Lemon juice 1  X 10-3 3 1  X 10-11 Orange juice, Vinegar, Gastric juices 1  X 10-4 4 1  X 10-10 Acid rain, Tomato juice, Soda 1  X 10-5 5 1  X 10-9 Rainwater (unpolluted), Black coffee 1  X 10-6 6 1  X 10-8 Milk, Urine, Saliva 1  X 10-7 7 Pure water 8 Egg whites 9 Baking Soda 10 Tums® (antacid) 11 Ammonia 12 Mineral Lime 13 Bleach, Oven cleaner 14 Drano®, NaOH (4%) How much more acidic is orange juice than coffee? The answer is the ratio of the concentrations of H3O+. Orange juice Coffee OJ is 100 times as acidic as coffee. This also implies that coffee is 100 times as basic as OJ.

Understanding pH Sources: 1. Anthony Carpi, Acids, Bases and pH, http://web.jjay.cuny.edu/~acarpi/NSC/7-ph.htm, 1998-1999 2. Paul Decelles, The pH Scale, http://staff.jccc.net/pdecell/chemistry/phscale.html, 6/20/2002