iii. ph
Post on 31-Dec-2015
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III. pHA. Dissociation of Water Molecules:
1. Water molecules split to form ions.
H2O H+ OH- + (hydroxide ion)
*The dissociation of water is reversible.
H+ + OH- H2O
3. Certain substances can cause imbalances in these concentrations.
2. In pure water, H+ and OH- are equal in concentration.
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. Bases1. Add more OH- when dissolved in water.
2. More OH- = stronger base
3. Alkaline
4. Taste bitter
• Example: NaOH Na+ and OH-
D. pH scaleThe measure of how acidic or
basic a compound is
7 1 2 3 4 5 6 8 9 10 11 12 13 14
Neutral
Acidic Basic
strong weak strongweak
[H+] > [OH-] [H+] < [OH-]
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