吸熱反応のデモンストレーション

水酸化バリウムとチオシアン酸アンモニウムの冷却反応

Thermochemistry Intermediate (High School) 20 分 ~$12.00

目的

フラスコ外部の水が凍るほど混合物が冷却される、劇的な吸熱反応を実証する。

背景

When barium hydroxide octahydrate reacts with ammonium thiocyanate, the temperature drops to approximately -20°C. This endothermic reaction absorbs so much heat from the surroundings that water on the outside of the flask freezes, effectively gluing the flask to a wet board.

安全上の警告

  • Barium compounds are toxic if ingested
  • Ammonia gas is released — work in fume hood or ventilated area
  • Wear gloves when handling barium hydroxide
  • Do not inhale the ammonia fumes

必要なPPE

goggles gloves lab_coat

材料

  • Barium hydroxide octahydrate (32 g)
    Toxic
  • Ammonium thiocyanate (16 g)
  • Water (5 mL)
    On the board

器具

250 mL Erlenmeyer flask Wooden board Thermometer Stirring rod

手順

1

Pour a few drops of water onto the wooden board to create a wet spot.

1 分
2

Add 32 g barium hydroxide octahydrate to the flask.

2 分 Wear gloves — barium is toxic
3

Add 16 g ammonium thiocyanate to the flask. Stir the mixture with a glass rod.

2 分 Ammonia released — ventilation
4

Place the flask on the wet spot on the board. Insert the thermometer.

1 分
5

Observe the temperature dropping dramatically. Record the minimum temperature.

5 分 Do not inhale fumes
6

After 5 minutes, try to lift the flask. It should be frozen to the board.

2 分
7

Explain that the reaction absorbed heat from the surroundings, freezing the water beneath.

2 分

予想される結果

The temperature should drop to approximately -20°C within minutes. The flask should freeze to the wet board. A strong smell of ammonia confirms the reaction is proceeding.

後片付け

Allow to warm to room temperature. Dispose of barium waste in heavy metal waste container. Rinse flask and ventilate area thoroughly.

詳細

カテゴリ
Thermochemistry
難易度
Intermediate (High School)
所要時間
20 分
推定費用
$12.00
ステップ数
7
材料
3

その他の実験

コーヒーカップ熱量測定 40 min コールドパックの化学 20 min ヘスの法則の検証 60 min マグネシウムの燃焼熱 50 min 氷の融解エンタルピー 25 min 溶解は常に発熱ではない 25 min 爆弾熱量測定シミュレーション 45 min 酢酸ナトリウムの発熱結晶化 30 min 金属の比熱容量 40 min

Frequently Asked Questions

What is the objective of 吸熱反応のデモンストレーション?
フラスコ外部の水が凍るほど混合物が冷却される、劇的な吸熱反応を実証する。
How difficult is 吸熱反応のデモンストレーション?
This experiment is rated as Intermediate (High School). It takes approximately 20 minutes to complete.
What safety precautions are needed for 吸熱反応のデモンストレーション?
Key safety precautions include: Barium compounds are toxic if ingested; Ammonia gas is released — work in fume hood or ventilated area; Wear gloves when handling barium hydroxide.
What materials are needed for 吸熱反応のデモンストレーション?
The main materials required are: Barium hydroxide octahydrate, Ammonium thiocyanate, Water.
What results should I expect from 吸熱反応のデモンストレーション?
The temperature should drop to approximately -20°C within minutes. The flask should freeze to the wet board. A strong smell of ammonia confirms the reaction is proceeding.