A conductivity apparatus is used to measure the equivalence point in a titration of barium hydroxide with sulfuric acid.

H2SO4(aq) + Ba(OH)2(aq)  →  BaSO4(s) + 2H2O(l)

Conductivity apparatus

To Conduct Demonstration:

  1.   With the conductivity meter lead in the stirring barium hydroxide solution, plug in the  conductivity meter.  It should indicate that the barium hydroxide solution conducts.
  2. Begin adding sulfuric acid from the buret.  Allow several seconds after each addition.
  3. As the titration progresses, insoluble barium sulfate will precipitate.  The solution will no longer conduct electricity and the diodes will all be dark and stay off in a range of approximately 1mL to either side of the endpoint.  The endpoint should take approximately 16 – 20 mL of 0.25M H2SO4 for a 2g sample of Ba(OH)2.8H2O.  Be very careful to go dropwise near the endpoint, as it is easy to overshoot it and never have the conductivity meter go completely dark.
  4.  Add excess sulfuric acid to show that the light will go back on.


Safety and Disposal

Goggles should be worn.

Care must be taken with the conductivity apparatus to prevent electrical shock.  Barium salts are hazardous.  A separate barium waste jug is in the demo room.