Chemie von Kältepacks

Untersuchung der endothermen Auflösung von Ammoniumnitrat

Thermochemistry Beginner (Middle School) 20 Min. ~$6,00

Ziel

Die Temperaturänderung bei der Auflösung von Ammoniumnitrat in Wasser messen und dabei einen endothermen Lösungsvorgang demonstrieren, wie er in Sofortkältepacks genutzt wird.

Hintergrund

Ammonium nitrate dissolves endothermically in water, absorbing heat from the surroundings and causing a significant temperature drop. This principle is used in commercial instant cold packs for first aid. The dissolution has ΔH = +25.7 kJ/mol.

Sicherheitswarnungen

  • Ammonium nitrate is an oxidizer — keep away from organic materials and heat
  • Do not mix with anything other than water for this experiment
  • Wear goggles

Erforderliche PSA

goggles

Materialien

  • Ammonium nitrate (NH₄NO₃) (30 g)
    Or from a commercial cold pack
  • Distilled water (100 mL)
    Room temperature

Ausrüstung

Polystyrene cup calorimeter Thermometer Stirring rod Analytical balance

Durchführung

1

Add 100 mL of distilled water to the polystyrene cup calorimeter. Record the initial temperature.

3 Min.
2

Weigh 30 g of ammonium nitrate.

2 Min. Ammonium nitrate is an oxidizer
3

Add the ammonium nitrate to the water. Stir gently to dissolve.

3 Min.
4

Record the temperature every 30 seconds as it drops. Note the minimum temperature.

5 Min.
5

Feel the outside of the cup — it should feel cold.

1 Min.
6

Calculate ΔH of dissolution per mole: q = mcΔT, n = mass/M(NH₄NO₃), ΔH = q/n.

5 Min.

Erwartete Ergebnisse

Temperature should drop 15-20°C. 30 g NH₄NO₃ = 0.375 mol. q = 100 × 4.18 × ΔT. Calculated ΔH should be approximately +25 kJ/mol (±15%).

Aufräumen

The ammonium nitrate solution is safe to dispose down the drain (dilute). Rinse the calorimeter.

Details

Kategorie
Thermochemistry
Schwierigkeit
Beginner (Middle School)
Dauer
20 Min.
Geschätzte Kosten
$6,00
Schritte
6
Materialien
2

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Frequently Asked Questions

What is the objective of Chemie von Kältepacks?
Die Temperaturänderung bei der Auflösung von Ammoniumnitrat in Wasser messen und dabei einen endothermen Lösungsvorgang demonstrieren, wie er in Sofortkältepacks genutzt wird.
How difficult is Chemie von Kältepacks?
This experiment is rated as Beginner (Middle School). It takes approximately 20 minutes to complete.
What safety precautions are needed for Chemie von Kältepacks?
Key safety precautions include: Ammonium nitrate is an oxidizer — keep away from organic materials and heat; Do not mix with anything other than water for this experiment; Wear goggles.
What materials are needed for Chemie von Kältepacks?
The main materials required are: Ammonium nitrate (NH₄NO₃), Distilled water.
What results should I expect from Chemie von Kältepacks?
Temperature should drop 15-20°C. 30 g NH₄NO₃ = 0.375 mol. q = 100 × 4.18 × ΔT. Calculated ΔH should be approximately +25 kJ/mol (±15%).