Química de las Bolsas de Frío

Estudio de la disolución endotérmica del nitrato de amonio

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

Objetivo

Medir el cambio de temperatura cuando el nitrato de amonio se disuelve en agua, demostrando un proceso de disolución endotérmico usado en bolsas de frío instantáneas.

Antecedentes

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.

Advertencias de seguridad

  • 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

EPP requerido

goggles

Materiales

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

Equipamiento

Polystyrene cup calorimeter Thermometer Stirring rod Analytical balance

Procedimiento

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

Resultados esperados

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%).

Limpieza

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

Detalles

Categoría
Thermochemistry
Dificultad
Beginner (Middle School)
Duración
20 min
Costo estimado
$6,00
Pasos
6
Materiales
2

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Frequently Asked Questions

What is the objective of Química de las Bolsas de Frío?
Medir el cambio de temperatura cuando el nitrato de amonio se disuelve en agua, demostrando un proceso de disolución endotérmico usado en bolsas de frío instantáneas.
How difficult is Química de las Bolsas de Frío?
This experiment is rated as Beginner (Middle School). It takes approximately 20 minutes to complete.
What safety precautions are needed for Química de las Bolsas de Frío?
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 Química de las Bolsas de Frío?
The main materials required are: Ammonium nitrate (NH₄NO₃), Distilled water.
What results should I expect from Química de las Bolsas de Frío?
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%).