Comparaison des Vitesses de Diffusion (Loi de Graham)

Comparaison des vitesses de diffusion des gaz HCl et NH₃

Gas Laws Intermediate (High School) 30 min ~$10,00

Objectif

Vérifier la loi de diffusion de Graham en comparant les vitesses de déplacement des gaz HCl et NH₃ dans un tube de verre.

Contexte

Graham's law states that the rate of diffusion of a gas is inversely proportional to the square root of its molar mass. When HCl (36.5 g/mol) and NH₃ (17 g/mol) diffuse toward each other in a tube, they form a white ring of NH₄Cl where they meet. The ring forms closer to the HCl end because NH₃ diffuses faster.

Avertissements de sécurité

  • Concentrated HCl fumes are corrosive and irritating
  • Concentrated ammonia fumes are irritating
  • Perform this experiment in a fume hood or well-ventilated area
  • Do not inhale either gas directly

EPI requis

goggles gloves lab_coat

Matériaux

  • Concentrated hydrochloric acid (5 mL)
    For HCl fumes
  • Concentrated ammonia solution (5 mL)
    For NH₃ fumes
  • Cotton wool (2 pieces)
    For soaking

Équipement

Glass tube (1 m long, 2 cm diameter) Rubber stoppers (2) Ruler Retort stand and clamps Stopwatch

Procédure

1

Clamp the glass tube horizontally on the retort stand.

3 min
2

In a fume hood, soak one cotton ball in concentrated HCl and another in concentrated ammonia.

2 min Fume hood — both gases are irritating
3

Simultaneously insert the HCl cotton ball into one end and the NH₃ cotton ball into the other end. Stopper both ends.

2 min Work quickly
4

Start the timer. Watch for a white ring of NH₄Cl to form where the two gases meet.

10 min
5

When the white ring appears, stop the timer. Measure the distance from each end to the ring.

3 min
6

Calculate the ratio of distances: d(NH₃)/d(HCl) should equal √(M(HCl)/M(NH₃)) = √(36.5/17) = 1.46.

5 min

Résultats attendus

The white NH₄Cl ring should form approximately 60% of the way from the HCl end (40% from the NH₃ end), since NH₃ diffuses 1.46 times faster than HCl. The ratio d(NH₃)/d(HCl) should be approximately 1.4-1.5.

Nettoyage

Remove cotton balls and dispose in fume hood. Rinse the glass tube with water. Ventilate the area.

Détails

Catégorie
Gas Laws
Difficulté
Intermediate (High School)
Durée
30 min
Coût estimé
$10,00
Étapes
6
Matériaux
3

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Frequently Asked Questions

What is the objective of Comparaison des Vitesses de Diffusion (Loi de Graham)?
Vérifier la loi de diffusion de Graham en comparant les vitesses de déplacement des gaz HCl et NH₃ dans un tube de verre.
How difficult is Comparaison des Vitesses de Diffusion (Loi de Graham)?
This experiment is rated as Intermediate (High School). It takes approximately 30 minutes to complete.
What safety precautions are needed for Comparaison des Vitesses de Diffusion (Loi de Graham)?
Key safety precautions include: Concentrated HCl fumes are corrosive and irritating; Concentrated ammonia fumes are irritating; Perform this experiment in a fume hood or well-ventilated area.
What materials are needed for Comparaison des Vitesses de Diffusion (Loi de Graham)?
The main materials required are: Concentrated hydrochloric acid, Concentrated ammonia solution, Cotton wool.
What results should I expect from Comparaison des Vitesses de Diffusion (Loi de Graham)?
The white NH₄Cl ring should form approximately 60% of the way from the HCl end (40% from the NH₃ end), since NH₃ diffuses 1.46 times faster than HCl. The ratio d(NH₃)/d(HCl) should be approximately 1.4-1.5.