1. pH and Buffers

2. Water Characteristics
The covalent bonds within the water molecule, like the hydrogen bonds between the molecules, can also break spontaneously. This is known as water dissociation.
H2O  H OH-
Water Hydrogen Ion Hydroxide Ion
This doesn’t happen often, but enough. If you have a beaker of pure water, 1/10,000,000 molecules are hydrogen ions.

3. pH
If you want to mathematically express the concentration of the hydrogen ions found in a solution, you would refer to the solution’s “pH”.

4. Key Features of pH Scale
 Acid, Base, Neutral Range
Acids are molecules that donate hydrogen ions to a solution.
In a chemical formula, acids start with “H”. Ex. HCl, HF (hydrochloric acid, hydrofluoric acid)
Bases are molecules that combine with hydrogen ions to remove them from a solution
In a chemical formula, end with “OH”. Ex. NaOH, KOH (sodium hydroxide, potassium hydroxide)
Scale is Logarithmic

5. Calculating pH: A couple key formulas:
[H+] + [OH-] = 1 x 10-14
pH + pOH = 14
If given the concentration, pH or pOH is simply the exponent on the 10.
Ex. [H+] = 1 x 10-2 the pH would be 2.
If given the pH, the [H+] would be calculated by making the pH value the negative exponent of the 10.
Ex pH = 9, [H+] = 1 x 10-9.

6. Why is pH important to living organisms?
Key molecules, known as enzymes, function at set pH values.
All our cells function within a certain pH range.
If the fluids bathing those cells is “off” these cells won’t function at max capacity.
Other than just cells, our blood needs to be at a certain pH.

7. But…
The chemical reactions of life constantly produce acids and bases within cells. These have a tendency to throw off the pH values. We need some sort of mechanism to minimize how much the pH is altered.

8. Solution
Buffers: substance that can take up or release hydrogen ions into a solution so that the pH can maintain equilibrium.
So...if pH is low, what about the [H+]?
It is HIGH
...if pH is high, what about the [H+]?
It is LOW

9. Buffers What would a buffer do if pH falls?
Remove hydrogen ions from the solution.
What would a buffer do if pH rises?
Donate hydrogen ions to the solution.
In living organisms a key buffer is known as the Bicarbonate Ion Buffer System.