La Disolución No Siempre Es Exotérmica

Comparación de cambios de temperatura de diferentes disoluciones de sales

Thermochemistry Beginner (Middle School) 25 min ~$8,00

Objetivo

Comparar la entalpía de disolución de diferentes sales (NaOH, CaCl₂, NH₄NO₃, KNO₃) para mostrar que la disolución puede ser exotérmica o endotérmica.

Antecedentes

Students often assume dissolving always releases heat. This experiment tests four salts: NaOH and CaCl₂ dissolve exothermically (temperature rises), while NH₄NO₃ and KNO₃ dissolve endothermically (temperature drops). The results illustrate that lattice energy vs hydration energy determines the sign of ΔH.

Advertencias de seguridad

  • NaOH is extremely corrosive
  • NH₄NO₃ is an oxidizer
  • Wear goggles and gloves

EPP requerido

goggles gloves

Materiales

  • Sodium hydroxide pellets (10 g)
    Exothermic
  • Calcium chloride (10 g)
    Exothermic
  • Ammonium nitrate (10 g)
    Endothermic
  • Potassium nitrate (10 g)
    Endothermic
  • Distilled water (400 mL)

Equipamiento

4 polystyrene cups Thermometer Stirring rod Analytical balance

Procedimiento

1

Add 100 mL water to each of four labeled cups. Record the initial temperature of each.

5 min
2

Add 10 g NaOH to cup 1. Stir and record the maximum temperature.

3 min Very exothermic — NaOH is corrosive
3

Add 10 g CaCl₂ to cup 2. Stir and record the maximum temperature.

3 min
4

Add 10 g NH₄NO₃ to cup 3. Stir and record the minimum temperature.

3 min
5

Add 10 g KNO₃ to cup 4. Stir and record the minimum temperature.

3 min
6

Create a table ranking the salts from most exothermic to most endothermic.

3 min
7

Discuss why some dissolve exothermically and others endothermically (lattice energy vs hydration energy).

5 min

Resultados esperados

NaOH: +15-20°C rise. CaCl₂: +10-15°C rise. NH₄NO₃: -15-20°C drop. KNO₃: -5-10°C drop. Clear demonstration that dissolution can be either exothermic or endothermic.

Limpieza

NaOH and CaCl₂ solutions should be neutralized before disposal. All solutions can be poured down the drain after dilution.

Detalles

Categoría
Thermochemistry
Dificultad
Beginner (Middle School)
Duración
25 min
Costo estimado
$8,00
Pasos
7
Materiales
5

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Frequently Asked Questions

What is the objective of La Disolución No Siempre Es Exotérmica?
Comparar la entalpía de disolución de diferentes sales (NaOH, CaCl₂, NH₄NO₃, KNO₃) para mostrar que la disolución puede ser exotérmica o endotérmica.
How difficult is La Disolución No Siempre Es Exotérmica?
This experiment is rated as Beginner (Middle School). It takes approximately 25 minutes to complete.
What safety precautions are needed for La Disolución No Siempre Es Exotérmica?
Key safety precautions include: NaOH is extremely corrosive; NH₄NO₃ is an oxidizer; Wear goggles and gloves.
What materials are needed for La Disolución No Siempre Es Exotérmica?
The main materials required are: Sodium hydroxide pellets, Calcium chloride, Ammonium nitrate, Potassium nitrate, Distilled water.
What results should I expect from La Disolución No Siempre Es Exotérmica?
NaOH: +15-20°C rise. CaCl₂: +10-15°C rise. NH₄NO₃: -15-20°C drop. KNO₃: -5-10°C drop. Clear demonstration that dissolution can be either exothermic or endothermic.