Lösen ist nicht immer exotherm

Vergleich der Temperaturänderungen bei verschiedenen Salzauflösungen

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

Ziel

Die Lösungsenthalpien verschiedener Salze (NaOH, CaCl₂, NH₄NO₃, KNO₃) vergleichen und zeigen, dass das Lösen exo- oder endotherm sein kann.

Hintergrund

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.

Sicherheitswarnungen

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

Erforderliche PSA

goggles gloves

Materialien

  • 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)

Ausrüstung

4 polystyrene cups Thermometer Stirring rod Analytical balance

Durchführung

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.

Erwartete Ergebnisse

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.

Aufräumen

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

Details

Kategorie
Thermochemistry
Schwierigkeit
Beginner (Middle School)
Dauer
25 Min.
Geschätzte Kosten
$8,00
Schritte
7
Materialien
5

Weitere Experimente

Bombenkalorimetrie-Simulation 45 min Chemie von Kältepacks 20 min Demonstration einer endothermen Reaktion 20 min Exotherme Kristallisation von Natriumacetat 30 min Kaffeebecher-Kalorimetrie 40 min Schmelzenthalpie von Eis 25 min Spezifische Wärmekapazität von Metallen 40 min Verbrennungswärme von Magnesium 50 min Verifikation des Hess'schen Gesetzes 60 min

Frequently Asked Questions

What is the objective of Lösen ist nicht immer exotherm?
Die Lösungsenthalpien verschiedener Salze (NaOH, CaCl₂, NH₄NO₃, KNO₃) vergleichen und zeigen, dass das Lösen exo- oder endotherm sein kann.
How difficult is Lösen ist nicht immer exotherm?
This experiment is rated as Beginner (Middle School). It takes approximately 25 minutes to complete.
What safety precautions are needed for Lösen ist nicht immer exotherm?
Key safety precautions include: NaOH is extremely corrosive; NH₄NO₃ is an oxidizer; Wear goggles and gloves.
What materials are needed for Lösen ist nicht immer exotherm?
The main materials required are: Sodium hydroxide pellets, Calcium chloride, Ammonium nitrate, Potassium nitrate, Distilled water.
What results should I expect from Lösen ist nicht immer exotherm?
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.