Ph & BUFFERS Notes: Ch. 3

pH & BUFFERS Notes: Ch. 3 KEY WORDS/ NOTES QUESTIONS Water *The covalent bonds within the water molecule, like the Characteristics 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. 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”.

KEY FEATURES OF SCALE: □ Acid, Base, Neutral Range o 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) o 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

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. Buffers Why is pH important to living organisms? Key molecules, known as enzymes, function at set pH pH & BUFFERS Notes: Ch. 3 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.

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.

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

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.