Production and Combustion of Acetylene
An attention-getting reaction is a good way to introduce writing and balancing
equations or working stoichiometry problems. This demonstration provides two
equations to balance, the first one easy and the second more challenging.
Of historical note is the use of the calcium carbide and water reaction to light lamps
used in the early days of mining and spelunking.
Chemicals and Equipment Needed
 d-H2O
 CaC2 – E3
o Use the chunks, not the powder; refill from the large container as needed.
 Modified pop bottle – Y1
o See below for alternative presentations
 Forceps – U2
 Candle-on-a-stick
 Matches – U1
 Weighboat – A3
Preparation
 Pour ~50 mL d-H2O into the base of the modified pop bottle. The top portion should fit easily into the
base
 Using forceps, pick out several pieces of CaC2 and place in weighboat for the lecturer. It is very
important that we keep moisture out of the main container.
Presentation
 Lift the top of the pop bottle, and pour the CaC2 inside. Replace the top
 Light the candle. Wait 15-20 seconds for gas to build up, then hold the candle over the hole in the top
of the bottle. The gas should ignite and the top will pop off. If desired, replace the top, wait for a
buildup of gases and light again.
Hazards:
 The combustion is explosive and blows the lid into the air with a significant amount of force, so the
reaction container should not be placed under light fixtures or anything breakable.
 Acetylene gas has a very unpleasant odor and is toxic when inhaled, so the reaction should be
performed in a well-ventilated room, or next to the in-bench hood. If acetylene is still being produced at
the end of the demonstration, place the container in the hood and keep it away from sources of ignition.
 It is imperative that the storage container for the CaC2 be kept free of moisture. Any utensils used to
remove the CaC2 from the container must be dry.
Clean-Up
 Set in the hood to continue reacting, if necessary. Flush the mixture of Ca(OH)2 and water down the
drain. Rinse the base of the container and reuse. Scrape any dripped wax off the top part of the
container
Revised Spring 2015
AMM
Acknowledgement: This demonstration was learned from Jerry Fensler of Defiance High School at the
Woodrow Wilson (Dreyfus) Workshop at OSU in 1989. Jerry also suggested various extensions of the
experiment, including drawing an energy profile diagram, calculating the volume of acetylene produced from a
given mass of calcium carbide, testing the product with phenolphthalein, etc.
NOTES: There are several variations of this demo:
 Use a 500 mL Erlenleyer flask with a side arm and a stopper. After adding the CaC2 to the water, the
gas produced is lit at the sidearm. Provided the stopper is not wedged in, the force of explosion will
blow the stopper off into the crowd.
 Place several chunks of CaC2 in the bottom of a Pyrex baking dish. Dump ice on top. As the ice melts,
acetylene will form. Light matches and toss onto ice, and they will light the gas so the ice appears to
burn.
 This demo can have some significant user error.
Revised Spring 2015
AMM