Voice Activated Reaction
- Page ID
- 131431
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Required Training |
Required PPE |
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UC Lab Safety Fundamentals |
Lab coat, safety glasses/goggles, nitrile gloves |
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Equipment |
Chemicals |
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Rubber stopper |
500 mL Erlenmeyer flask |
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250 mL DI water |
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1 drop of 1N NaOH |
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10 drops of phenol red indicator |
Procedure:
- Add all the chemicals together in the flask and stopper immediately to protect the solution from atmospheric CO2. The solution should be red at this point.
- Announce to the classroom that this reaction can be activated by voice, if the person has just the right voice.
- Pass the flask around and have each student unstopper it, politely ask the solution to change color, stopper the flask and swirl before passing it to the next student.
- Another option is to blow into the flask. This will speed up the reaction.
Discussion:
CO2 from the students’ breath will produce enough acid in the solution to lower the pH and change the color to yellow.
CO2 (g) + H20 (l) → H2CO3 (aq) ↔ H+ (aq) + HCO3- (aq)
CO2 also reacts with NaOH to produce Na2CO3
2NaOH (aq) + CO2 (g) → Na2CO3 (aq) + H2O (l)
Hazards:
If skin comes in contact with sodium hydroxide, wash affected water with copious water.
SOP: 
Carcinogen – Phenolphthalein
Corrosive – Sodium Hydroxide
Reproductive Hazard – Phenolphthalein
Disposal (by Storeroom)
N/A