Cristallisation Exothermique de l'Acétate de Sodium

Mesure de la chaleur dégagée lors de la cristallisation instantanée

Thermochemistry Intermediate (High School) 30 min ~$8,00

Objectif

Quantifier la chaleur dégagée lors de la cristallisation de l'acétate de sodium sursaturé par calorimétrie.

Contexte

When supersaturated sodium acetate crystallizes, it releases stored energy as heat. By triggering crystallization inside a calorimeter and measuring the temperature rise, the enthalpy of crystallization can be determined. This is the same principle used in reusable hand warmers.

Avertissements de sécurité

  • Hot solution during preparation
  • Crystallization releases heat — container gets warm

EPI requis

goggles

Matériaux

  • Sodium acetate trihydrate (80 g)
  • Distilled water (150 mL)

Équipement

Polystyrene cup calorimeter Hot plate Thermometer Beaker (250 mL) Stirring rod

Procédure

1

Dissolve 80 g sodium acetate trihydrate in 20 mL water by heating to about 70°C. Stir until clear.

8 min Handle hot solution carefully
2

Pour the solution into the polystyrene cup calorimeter. Allow to cool undisturbed to room temperature.

15 min
3

Record the temperature of the supersaturated solution.

1 min
4

Add a single small crystal of sodium acetate to trigger crystallization. Immediately stir gently and record temperature every 15 seconds.

3 min
5

Record the maximum temperature reached.

1 min
6

Calculate the heat released: q = mcΔT. Determine ΔH of crystallization per mole.

5 min

Résultats attendus

Temperature should rise 15-25°C above room temperature. The enthalpy of crystallization is approximately -19.7 kJ/mol for sodium acetate trihydrate. Measured values should be within 20% of this.

Nettoyage

The sodium acetate can be remelted and reused. Rinse the calorimeter. Non-toxic — can go down the drain.

Détails

Catégorie
Thermochemistry
Difficulté
Intermediate (High School)
Durée
30 min
Coût estimé
$8,00
Étapes
6
Matériaux
2

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Frequently Asked Questions

What is the objective of Cristallisation Exothermique de l'Acétate de Sodium?
Quantifier la chaleur dégagée lors de la cristallisation de l'acétate de sodium sursaturé par calorimétrie.
How difficult is Cristallisation Exothermique de l'Acétate de Sodium?
This experiment is rated as Intermediate (High School). It takes approximately 30 minutes to complete.
What safety precautions are needed for Cristallisation Exothermique de l'Acétate de Sodium?
Key safety precautions include: Hot solution during preparation; Crystallization releases heat — container gets warm.
What materials are needed for Cristallisation Exothermique de l'Acétate de Sodium?
The main materials required are: Sodium acetate trihydrate, Distilled water.
What results should I expect from Cristallisation Exothermique de l'Acétate de Sodium?
Temperature should rise 15-25°C above room temperature. The enthalpy of crystallization is approximately -19.7 kJ/mol for sodium acetate trihydrate. Measured values should be within 20% of this.