Calcium Carbide and Water

The two anions of carbon, the carbide (C4-) and dicarbide (C22-) ions react with water to produce hydrocarbons. The carbide ion gives methane gas, and the dicarbide ion gives acetylene gas. This video shows the reaction between calcium carbide and water to produce acetylene and calcium hydroxide. Acetylene is combustible, and burns when ignited.

CaC2(s) + H2O(l) = Ca(OH)2(aq) + C2H2(g)

Pieces of calcium carbide are added to a flask contaning water A rubber stopper fitted with glass tubing is added. Solution has turned cloudy due to the formation of insoluble calcium hydroxide. Bubbling is observed due to the release of acetylene gas.
The "torch" is lighted The acetylene burns independently

Hazards: This reaction is typically fairly benign. However, one once did explore (the air-acetylene mixture must have been just right) so caution is justified. The combustion of the acetlyne produces a lot of soot, not visible in the video, and so a fume hood is recommended.

Download the video here
(Windows AVI format, Video9 compression)

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