Реакция иодных часов

Реакция с задержкой, внезапно темнеющая до тёмно-синего цвета через предсказуемое время

Classroom Demonstrations Intermediate (High School) 45 мин ~$10,00

Цель

Показать кинетику реакций и влияние концентрации и температуры на скорость реакции с помощью реакции иодных часов.

Предпосылки

The iodine clock reaction is a classic demonstration of chemical kinetics. Two colorless solutions are mixed and after a predictable delay, the solution suddenly turns dark blue. The delay occurs because bisulfite (HSO₃⁻) rapidly reduces any I₂ produced back to I⁻ (the clock mechanism). When all the bisulfite is consumed, I₂ accumulates and reacts with starch to produce the dramatic blue-black color. By varying concentration or temperature, students can explore factors affecting reaction rate.

Предупреждения по безопасности

  • H₂SO₄ is corrosive
  • NaHSO₃ releases SO₂ gas if over-acidified — work in ventilated area
  • KIO₃ is an oxidizer
  • Hot plate surfaces are a burn hazard

Требуемые СИЗ

goggles gloves lab_coat

Материалы

  • Potassium iodate (KIO₃) (2 g)
    Solution A
  • Sodium bisulfite (NaHSO₃) (1 g)
    Solution B
  • Starch solution (1%) (10 mL)
    Indicator in Solution B
  • Sulfuric acid (0.5M H₂SO₄) (20 mL)
    Solution A acidification
  • Distilled water (500 mL)

Оборудование

Beakers (250 mL, 4) Magnetic stirrer Stopwatch Thermometer Graduated cylinders Hot plate Ice bath

Процедура

1

Prepare Solution A: Dissolve 2 g KIO₃ in 200 mL water, add 20 mL of 0.5M H₂SO₄.

5 мин
2

Prepare Solution B: Dissolve 1 g NaHSO₃ in 200 mL water, add 10 mL of 1% starch solution.

5 мин
3

Trial 1 (baseline): Mix 50 mL of A with 50 mL of B and start the stopwatch immediately. Record the time until the solution turns blue.

5 мин
4

Trial 2 (concentration effect): Mix 25 mL of A + 25 mL water with 50 mL of B. Record the time. It should take approximately twice as long.

7 мин
5

Trial 3 (temperature effect): Warm both solutions to 40°C. Mix 50 mL of each and record the time. It should be significantly shorter.

8 мин Handle warm solutions carefully
6

Trial 4 (cold): Cool both solutions to 10°C in an ice bath. Mix and record the time.

8 мин
7

Plot reaction time vs. concentration and temperature. Discuss rate law, activation energy, and the Arrhenius equation.

7 мин

Ожидаемые результаты

The blue color appears suddenly after a delay of 5–60 seconds depending on conditions. Doubling concentration roughly halves the time. Increasing temperature by 10°C roughly halves the time (consistent with the Arrhenius equation).

Уборка

Pour reacted solutions down the drain with water. Rinse all glassware. Clean the magnetic stirrer.

Детали

Категория
Classroom Demonstrations
Сложность
Intermediate (High School)
Продолжительность
45 мин
Прим. стоимость
$10,00
Шаги
7
Материалы
5

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Frequently Asked Questions

What is the objective of Реакция иодных часов?
Показать кинетику реакций и влияние концентрации и температуры на скорость реакции с помощью реакции иодных часов.
How difficult is Реакция иодных часов?
This experiment is rated as Intermediate (High School). It takes approximately 45 minutes to complete.
What safety precautions are needed for Реакция иодных часов?
Key safety precautions include: H₂SO₄ is corrosive; NaHSO₃ releases SO₂ gas if over-acidified — work in ventilated area; KIO₃ is an oxidizer.
What materials are needed for Реакция иодных часов?
The main materials required are: Potassium iodate (KIO₃), Sodium bisulfite (NaHSO₃), Starch solution (1%), Sulfuric acid (0.5M H₂SO₄), Distilled water.
What results should I expect from Реакция иодных часов?
The blue color appears suddenly after a delay of 5–60 seconds depending on conditions. Doubling concentration roughly halves the time. Increasing temperature by 10°C roughly halves the time (consistent with the Arrhenius equation).