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Conductivity Change of Acetic Acid with Dilution

Chemicals and Solutions

  • 1.0 M Acetic acid
  • Glacial Acetic acid

Materials

  • 2 - 400 ml beakers
  • Single conductivity apparatus with large carbon filament bulb

Procedure

  1. Fill one beaker half full of glacial acetic acid and test it with the conductivity apparatus. The light bulb does not light up. Glacial acetic acid does not dissociate enough to be able to conduct electricity.
  2. Now fill the other beaker half full of 1.0 M acetic acid and test it with the conductivity apparatus. The bulb will light up.
  3. Place a small amount of (about 20 mL) glacial acetic acid in a 400 mL beaker and test its conductivity.
  4. Dilute the glacial acetic acid with lots of water such that the solution will conduct.

\( \ce{ CH3COOH + H2O <=> CH3COO- + H3O+ } \)

Adding water shifts the equilibrium to the right so that more ions are formed and the solution conducts electricity. (Eventually, the acetic acid becomes too dilute and conductivity drops off again.)

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