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  1. How do we use pH indicators?
  2. Indicator: definition and examples.
  3. Using equilibrium (Le Chatelier's principle) with indicators.
  4. Using equilibrium (Keq) with indicators
  5. Testing relative strength of acids: example.
  1. Understand how the colour change of pH indicators is related to acid-base chemistry.
    Alizarin yellow is a pH indicator which is yellow when protonated and blue when deprotonated.
    1. Write a Ka expression and equilibrium equation showing the dissociation of alizarin yellow, using the symbols HIn and In-.
    2. In terms of equilibrium concentration, what happens to the pH indicator at the titration endpoint?
    3. Explain, in terms of equilibrium, why the solution turns yellow when [H3O+] is high.