2. What are indicators?What are indicators?  Contains a weak acid and its conjugate base  Weak acid—one color  Conjugate base—different color  Changes color based on what solution (acidic or basic) it is placed in.  Color within a solution is dependent on the amount of acid and conjugate base----SO pH dependent.  Used when specific pH measurements not needed

3. How do indicators work?How do indicators work?  HIn + H 2 O  H 3 O + + In - (yellow) (red)  Acidic Solution —  Yellow color is seen, reaction shifts to the LEFT  Basic Solution —  Red color is seen, reaction shifts to the RIGHT  Neutral Solution  Same concentration of indicator acid/anion  Color mixture between the two colors

4. Common IndicatorsCommon Indicators  Phenolphthalein  Litmus indicator  Broad pH range  Litmus—  Dye originating from lichens  pH 8.3 (blue)

5. Indicators and TitrationsIndicators and Titrations  pH rapidly shifts past the equivalence point  Shift affects indicator equilibrium—creates a color change  Different indicators have different pH ranges where equilibrium changes (color change)  Select indicator changing color close to the pH at the equivalence point.