Oszillierende Briggs-Rauscher-Reaktion

Eine chemische Uhr, die zwischen farblos, bernsteinfarben und tiefblau wechselt

Classroom Demonstrations Advanced (University) 40 Min. ~$20,00

Ziel

Eine chemisch oszillierende Reaktion beobachten, die wiederholt zwischen drei verschiedenen Farbzuständen wechselt, und dabei nichtlineare chemische Kinetik demonstrieren.

Hintergrund

The Briggs-Rauscher reaction is one of the most visually stunning demonstrations of oscillating chemical kinetics. Three solutions are mixed, and the resulting solution spontaneously cycles between colorless, amber, and deep blue states for several minutes. The oscillations occur because two competing reaction pathways alternately dominate: a radical pathway (producing I₂, which reacts with starch to form the blue color) and a non-radical pathway (consuming I₂, clearing the blue).

Sicherheitswarnungen

  • 30% H₂O₂ causes burns — handle with extreme care
  • H₂SO₄ is corrosive
  • KIO₃ is an oxidizer
  • Wear face shield during mixing step
  • Do not lean over the reaction vessel

Erforderliche PSA

goggles gloves lab_coat

Materialien

  • Potassium iodate (KIO₃) (4.3 g)
    Solution A component
  • Malonic acid (CH₂(COOH)₂) (1.6 g)
    Solution B component
  • Manganese(II) sulfate (MnSO₄) (0.4 g)
    Solution B catalyst
  • Starch solution (1%) (5 mL)
    Solution B indicator
  • Hydrogen peroxide (30%) (50 mL)
    Solution C
  • Sulfuric acid (1M H₂SO₄) (20 mL)
    Solution A acidification
  • Distilled water (500 mL)

Ausrüstung

Beakers (500 mL, 3 for solutions + 1 for mixing) Magnetic stirrer and stir bar Graduated cylinders White background paper

Durchführung

1

Prepare Solution A: Dissolve 4.3 g KIO₃ in 100 mL warm water. Add 20 mL of 1M H₂SO₄.

5 Min. Handle acid carefully
2

Prepare Solution B: Dissolve 1.6 g malonic acid and 0.4 g MnSO₄ in 100 mL water. Add 5 mL of 1% starch solution.

5 Min.
3

Prepare Solution C: Dilute 50 mL of 30% H₂O₂ to 100 mL with water.

3 Min. 30% H₂O₂ is corrosive
4

Set the magnetic stirrer to moderate speed. Pour all three solutions simultaneously into the large beaker on the stirrer.

2 Min. Step back after mixing
5

Observe: the solution cycles colorless → amber → deep blue → colorless, repeating for 5–15 minutes. Time the oscillation period.

15 Min.
6

Record the number of oscillations and the period of each cycle. Note how the period changes over time.

5 Min.
7

Discuss the mechanism: competing radical and non-radical pathways, the role of iodine and starch, and the concept of chemical oscillators.

5 Min.

Erwartete Ergebnisse

The solution oscillates between colorless, amber, and deep blue 10–15 times before settling to a permanent dark blue. Each oscillation takes 10–30 seconds initially, with the period increasing as reactants are consumed.

Aufräumen

The spent solution contains iodine and manganese. Collect in inorganic waste. Rinse all glassware. Clean the magnetic stir bar.

Details

Kategorie
Classroom Demonstrations
Schwierigkeit
Advanced (University)
Dauer
40 Min.
Geschätzte Kosten
$20,00
Schritte
7
Materialien
7

Weitere Experimente

Chemilumineszenz mit Luminol 30 min Dichtesäulen-Regenbogen 30 min Elefantenzahnpasta 20 min Iod-Uhr-Reaktion 45 min Nicht-newtonsche Flüssigkeit: Oobleck 20 min Reaktion von Natrium und Wasser 25 min Sofortgefrieren: unterkühltes Wasser 120 min Thermit-Reaktion 30 min Verbrennung von Magnesium in Trockeneis 25 min Verschwindender Becher (Brechungsindexanpassung) 15 min

Frequently Asked Questions

What is the objective of Oszillierende Briggs-Rauscher-Reaktion?
Eine chemisch oszillierende Reaktion beobachten, die wiederholt zwischen drei verschiedenen Farbzuständen wechselt, und dabei nichtlineare chemische Kinetik demonstrieren.
How difficult is Oszillierende Briggs-Rauscher-Reaktion?
This experiment is rated as Advanced (University). It takes approximately 40 minutes to complete.
What safety precautions are needed for Oszillierende Briggs-Rauscher-Reaktion?
Key safety precautions include: 30% H₂O₂ causes burns — handle with extreme care; H₂SO₄ is corrosive; KIO₃ is an oxidizer.
What materials are needed for Oszillierende Briggs-Rauscher-Reaktion?
The main materials required are: Potassium iodate (KIO₃), Malonic acid (CH₂(COOH)₂), Manganese(II) sulfate (MnSO₄), Starch solution (1%), Hydrogen peroxide (30%).
What results should I expect from Oszillierende Briggs-Rauscher-Reaktion?
The solution oscillates between colorless, amber, and deep blue 10–15 times before settling to a permanent dark blue. Each oscillation takes 10–30 seconds initially, with the period increasing as reactants are consumed.