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III. pH. A. Dissociation of Water Molecules:. 1. Water molecules split to form ions. (hydroxide ion). H 2 O. H +. +. OH -. H +. +. OH -. *The dissociation of water is reversible. H 2 O. 2. In pure water, H + and OH - are equal in concentration.
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III. pH A. Dissociation of Water Molecules: 1. Water molecules split to form ions. (hydroxide ion) H2O H+ + OH-
H+ + OH- *The dissociation of water is reversible. H2O
2. In pure water, H+ and OH- are equal in concentration. 3. Certain substances can cause imbalances in these concentrations. a. These substances are called ACIDS and BASES.
B. Acids 1. Add (donate) more H+ when dissolved in water. 2. More H+ = stronger acid 3. Taste sour • Example: HCl H+ and Cl-
C. Bases 1. Add more OH- when dissolved in water. 2. More OH- = stronger base 3. Alkaline 4. Taste bitter • Example: NaOH Na+ and OH-
D. pH scale The measure of how acidic or basic a compound is Neutral 7 1 2 3 4 5 68 9 10 11 12 13 14 strong weak weak strong Basic Acidic [H+] > [OH-] [H+] < [OH-]