Presentation on theme: "PH and Buffers. Water Characteristics The covalent bonds within the water molecule, like the hydrogen bonds between the molecules, can also break spontaneously."— Presentation transcript:
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.
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 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
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.
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.
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.
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
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.