Crushed ice is covered over the bottom of a beaker.
Calcium carbide (CaC2) is sprinkled over the ice.
A match is dropped into the beaker.
Chemical Concept Demonstrated: chemistry of alkynes
Demonstration:
Crushed ice is covered over the bottom of a beaker. Calcium carbide (CaC2) is sprinkled over the ice. A match is dropped into the beaker. |
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Observations:
An exothermic reaction occurs.
Explanation (including important chemical equations):
Calcium carbide reacts with water to form acetylene.
CaC2 (s) + H2O (l) --> Ca2+ (aq) +2 OH- (aq) + H2C2 (g)
In the presence of a flame, acetylene reacts with oxygen to form carbon dioxide and water.
2 H2C2 (g) + 5 O2 (g) --> 4 CO2 (g) + 2 H2O (g)
Because of the visual display, this demonstration is sometimes referred to as "fire rocks" (see demonstration 5.20k).
Additional calcium carbide/acetylene chemistry can be seen in the carbide cannon demonstration (see demonstration 5.20j).