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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