ヨウ素時計反応

予測可能な遅延後に突然深青色に変わる時間制御反応

Classroom Demonstrations Intermediate (High School) 45 分 ~$10.00

目的

ヨウ素時計反応を使って反応動力学と濃度・温度が反応速度に与える影響を実証する。

背景

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.

安全上の警告

  • 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

必要なPPE

goggles gloves lab_coat

材料

  • 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)

器具

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

手順

1

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

5 分
2

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

5 分
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 分
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 分
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 分 Handle warm solutions carefully
6

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

8 分
7

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

7 分

予想される結果

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).

後片付け

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

詳細

カテゴリ
Classroom Demonstrations
難易度
Intermediate (High School)
所要時間
45 分
推定費用
$10.00
ステップ数
7
材料
5

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Frequently Asked Questions

What is the objective of ヨウ素時計反応?
ヨウ素時計反応を使って反応動力学と濃度・温度が反応速度に与える影響を実証する。
How difficult is ヨウ素時計反応?
This experiment is rated as Intermediate (High School). It takes approximately 45 minutes to complete.
What safety precautions are needed for ヨウ素時計反応?
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 ヨウ素時計反応?
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 ヨウ素時計反応?
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).