1 M NaOH is added incrementally to beakers containing DI water, and 0.01 M, 0.1 M, and 1 M acetate buffer solutions to which universal indicator has been added. The DI water changes dramatically with the addition of a single drop. The 1 M buffer solution, on the other hand, has to be transferred to a larger beaker to accommodate the acid/base addition before it begins to change!
This demo is good for showing buffer capacity in a general chemistry class. About 10-15 minutes.
This demo has a great "wow" factor. I like to ham it up by acting like I'm getting bored with adding the acid or base dropwise, and then add it by the dropperful. Then I get bored with adding it by the dropperful and pour directly from the dropper bottle. When that runs out, I pull out the 250 mL bottle and start pouring from that.
As described above.
- 4 ea. 150 mL beakers containing 100 mL of the following solutions: 0.5 M Acetic Acid/0.5 M Sodium Acetate, 0.05 M Acetic Acid/0.05 M Sodium Acetate, 0.005 M Acetic Acid/0.005 M Sodium Acetate, each with a couple of dropperfuls of universal indicator solution added and a stir bar in the beaker.
- stir plate
- 1 ea. large dropper bottle of 1 M NaOH.
- 1 ea. 250 mL bottle containing 1 M NaOH.
- 1 ea. 400 mL beaker containing a stir bar.
- Place the beaker of DI water on the stir plate and turn on and adjust the stir plate.
- Add a couple of drops of 1 M NaOH to the solution until it changes to violet.
- Repeat with the remaining solutions, proceeding to the next higher buffer concentration each time. it will require more and more base to effect the change each time.
- By the time you get to the IM buffer solution, you will need to transfer the solution to the 400 mL beaker to accomplish the change.
- Always wear goggles when performing chemistry demonstrations.
- If you get base on your hands, rinse thoroughly with water.
- I you get base in your eyes flush with copious amounts of water.
As described above.