• An acid-base indicator displays different colors when in the presence of an acid or a base.
  • An indicator is a weak acid that ionizes within a known pH range, usually about 2 pH units.
  • To be useful as an indicator, the two forms must be different colors.
  • Universal indicator displays the entire rainbow of colors from low pH to high pH (see Figure below).
  • Universal indicator is used to make pH paper, which can be used to quickly test solutions for their approximate pH.
  • Use the resource below to answer the questions that follow.
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