Rate of Diffusion: The Ammonium Chloride Ring
Description: Ammonia gas and hydrogen chloride gas are introduced at opposite ends of a long air-filled glass tube. After about 15-20 minutes, a very localized cloud of white ammonium chloride forms where the two gases meet after diffusing through the air. The location is relative to the molecular masses of two gases.
Source: Shakhashiri, B.Z. Chemical Demonstrations: A Handbook for Teachers of Chemistry
Year: 1985 Vol: 2 Page: 59
Keywords: Diffusion; Graham’s Law, Kinetic Molecular Theory, Molecular speeds, Path length
Rating: 
Hazard: Medium
- Acute toxicity hazard – inhalation, ingestion, oral
- Serious eye damage
- Skin corrosion hazard
- Specific exposure hazard to the eye, lungs
- Aquatic toxicity hazard
- Corrosive to metals
- Spill hazard
Effectiveness: Good
- Good connection from demo to course material
- Some contrast between behavior of systems
- Time to results is high, greater than 20 minutes
- Moderate failure rate
- Results are observable with guidance
Difficulty: Medium
- Some concerted or timed manipulations
- Use of reactive substances
- Simultaneous manipulations
- Demos at non-standard conditions
- Prior training required
- Simple procedures
Safety Precautions:
- Eye protection required
- Gloves required
- Perform in a well-ventilated area
- Chemically resistant surface required
- Downdraft hood recommended
- Absorbent material on hand
- Sodium bicarbonate solution on hand
- Prevent release of reagents to the environment
Class: Gases, Acid-Base Reaction, Kinetics
Division: General, Physical Chemistry
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