This experiment is for advanced students. All chemical reactions are equilibrium reactions. This experiment is really cool because you’re going to watch how a chemical reaction resists a pH change.


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Materials:


  • baking soda
  • universal indicator
  • distilled white vinegar
  • 3 test tubes with stoppers
  • distilled water
  • medicine droppers
  • clear soda
  • safety goggles and gloves


  1. First add water to a test tube and then add 10 drops of universal indicator and shake it up.
  2. Compare the color with your color chart and find the pH number. Set aside.
  3. Into a second test tube, add baking soda and water. Shake it up again!
  4. Add 10 drops universal indicator and shake the second test tube up again.
  5. Compare the second test tube with the pH chart to find the number.
  6. Using your medicine dropper, place soda to the second test be and look for a color change.
  7. Keep adding dropper-fulls of soda until you get the pH to match the first test tube (7).
  8. Add two drops of distilled white vinegar and look for a color change. Add more drops as needed.
  9. What happened?

We had two solutions that were both around 7. When we added an acid to one of them, the pH should have decreased. But why when we added the acid to the baking soda-carbonated soda solution, did it not change at all? That’s because it’s a buffer solution, which resists changes in pH.


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Comments

6 Responses to “Bicarbonate Buffer”

  2. carmen_schmitz says:

    Where can we buy these chemistry sets in Canada? I’m having a hard time finding a site in Canada or a site able to ship to Canada. Thanks. (particularly C3000 v 2.0)

  3. Yes, that’s right. Universal indicator is actually a solution of lots of different compounds make the color change more of a smooth progression than the anthocyanin in the red cabbage juice (and the colors will be different pH levels), but the idea is the same.

  4. Michelle Palmer says:

    So if I just take a purple cabbage and boil it to get the color that is the same thing as the universal indicator?

  5. You can make some from purple cabbage juice, or you can buy it inexpensively here.

  6. Robyn Schwetz says:

    ??? In our C3000 kit there is no universal indicator. What exactly is it and any recommends on where to get some so we can do the bicarbonate buffer experiment? Thank you!