pH Relative concentration of H + ions in water HOH ↔ H + + OH - O HH

pH Relative concentration of H + ions in water HOH ↔ H + + OH - Equilibrium of: –Water (HOH or H 2 O) –Hydrogen ion (H + ) –Hydroxide ion (OH - ) Acid –Low pH (high H + ) Base (alkaline) –High pH (low H + ) Neutral –pH = 7.00 (H + = OH - ) Acidic Basic Neutral

pH Litmus test –Red is acid –Blue is base Still used as color code for acids/bases NOT precise, however Acidic Basic Neutral Color transition zone

pH Buffers –Chemicals that absorb excess acids and bases added to the solution –Buffered solutions do not change in pH (very much) when acids or bases are added –Buffers can be used up Redundancy –Multiple mechanisms –Maximizes safety Acidic Basic Neutral