demonstrations:acetylene_from_calcium_carbide
Acetylene From Calcium Carbide
Materials: ★★★ Requires materials not commonly found in school laboratories
Difficulty: ★★★ Requires a more experienced teacher
Safety: ★★★ Only to be attempted with adequate safety procedures and trained staff
Categories: Combustion, Gases
Alternative titles: Combustion of Acetylene
Summary
Acetylene gas is generated by reacting calcium carbide with hydrochloric acid.
Procedure
- Place small pieces of calcium carbide in a flask fitted with a delivery tube.
- Add water slowly to the flask to initiate the reaction.
- Collect the gas evolved (acetylene) by downward displacement of water.
- Use the gas immediately, as acetylene is unstable and highly flammable.
Links
Laboratory Preparation of Acetylene (C2H2) Gas | CBSE Syllabus - Practical Science:
Lab. preparation of ACETYLENE gas - Practical CHEMISTRY | Flammable Gas - Science Sir:
📄 Spontaneous Combustion of Acetylene - UC San Diego: https://www-chem.ucsd.edu/undergraduate/teaching-labs/demos/demo22.html
Variations
- Show the combustion of acetylene in air to demonstrate its sooty flame.
- Compare acetylene combustion with methane combustion to highlight differences between alkyne and alkane burning.
- Use acetylene in a reaction with chlorine (under safe, controlled conditions) to illustrate reactivity.
Safety Precautions
- Wear safety goggles, gloves, and a lab coat.
- Handle calcium carbide carefully; it reacts violently with water to release flammable gas.
- Perform the reaction in a well-ventilated area or fume hood.
- Keep all flames and ignition sources away from acetylene until intended combustion.
- Dispose of calcium hydroxide residue safely as basic waste.
Questions to Consider
- What happens when CaC₂ reacts with water? (It produces acetylene gas and calcium hydroxide.)
- What is the balanced chemical equation? (CaC₂ + 2H₂O → C₂H₂ + Ca(OH)₂.)
- What type of chemical reaction is this? (Hydrolysis reaction.)
- What are some uses of acetylene gas? (Welding, production of organic compounds, laboratory demonstrations.)
- Why must acetylene be collected and used immediately? (It is unstable and highly flammable.)