2. Acids, Bases and pH

3. Water molecules dissociate Dissociates into OH- and H+ Water is neutral because there are equal numbers of OH- and H+

4. pH Scale The number of H+ ions present is the basis of the pH scale. How many H+ ? 1 x 10 (-7) is neutral The greater the H+ concentration, the lower the pH

5. Factors of 10 1 x 10 (-6) is 10 times more H+ ions than 1 x 10 (-7), and the pH is 6. This is a stronger acid The greater the H+ ion concentration, the lower the pH Acids donate H+ ions when dissolved in water

6. The Bases Above 7 on the pH scale is considered to be basic. This would mean fewer H+ ions are present. These substances accept H+ ions when dissolved in water. OH- forms

7. Buffers A substance that acts as a reservoir for H+ ions. Donates them to the solution when their concentration falls, and takes them out when concentration rises.

8. Buffer in Blood Carbonic acid and bicarbonate Work as a buffer system to keep blood pH constant Interact in a reversible reaction CO 2 + H 2 0----H 2 CO 3 H 2 CO 3, which is carbonic acid can become HCO 3 - + H+, which is bicarbonate ion plus hydrogen ions.

9. If H+ is added to blood, goes to carbonic acid CO 2 + H 2 O H 2 CO 3 If base removes H+, H 2 CO 3 dissociates, releasing more H+. Stabilizes blood pH; normal blood pH is 7.4

10. Salts Compounds that release ions other than H+ and OH-. Many release ions crucial to cell function For example, Na+, K+ for nerve action, and Ca+ for muscle contraction