Осциллирующая реакция Бриггса–Раушера

Химические часы, циклически меняющие цвет: бесцветный, янтарный, тёмно-синий

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

Цель

Наблюдать химическую осциллирующую реакцию, многократно проходящую через три различных цветовых состояния, и продемонстрировать нелинейную химическую кинетику.

Предпосылки

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).

Предупреждения по безопасности

  • 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

Требуемые СИЗ

goggles gloves lab_coat

Материалы

  • 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)

Оборудование

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

Процедура

1

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

5 мин 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 мин
3

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

3 мин 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 мин Step back after mixing
5

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

15 мин
6

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

5 мин
7

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

5 мин

Ожидаемые результаты

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.

Уборка

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

Детали

Категория
Classroom Demonstrations
Сложность
Advanced (University)
Продолжительность
40 мин
Прим. стоимость
$20,00
Шаги
7
Материалы
7

Ещё эксперименты

Горение магния в сухом льду 25 min Исчезающий стакан (совмещение показателей преломления) 15 min Мгновенное замерзание: переохлаждённая вода 120 min Неньютоновская жидкость: оублек 20 min Радуга из столбиков жидкостей разной плотности 30 min Реакция иодных часов 45 min Реакция натрия с водой 25 min Слоновья зубная паста 20 min Термитная реакция 30 min Хемилюминесценция с люминолом 30 min

Frequently Asked Questions

What is the objective of Осциллирующая реакция Бриггса–Раушера?
Наблюдать химическую осциллирующую реакцию, многократно проходящую через три различных цветовых состояния, и продемонстрировать нелинейную химическую кинетику.
How difficult is Осциллирующая реакция Бриггса–Раушера?
This experiment is rated as Advanced (University). It takes approximately 40 minutes to complete.
What safety precautions are needed for Осциллирующая реакция Бриггса–Раушера?
Key safety precautions include: 30% H₂O₂ causes burns — handle with extreme care; H₂SO₄ is corrosive; KIO₃ is an oxidizer.
What materials are needed for Осциллирующая реакция Бриггса–Раушера?
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 Осциллирующая реакция Бриггса–Раушера?
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.