C2H2 has a straight-line molecular geometry consisting of a hydrogen atom bonded to a carbon atom, which is triple-bonded to a second carbon atom bonded to a second hydrogen atom. The common name for this molecule is acetylene.
Acetylene forms an explosive gas in the presence of air. The triple bond of the molecule stores a large amount of energy that readily oxidizes to form a more stable molecule. This oxidation occurs rapidly, and the release of energy is an explosion. Acetylene is a common gas for fueling welders' oxyacetylene torches. When dissolved in acetone, acetylene becomes much less explosive. The gas cylinders one finds in welding shops contain this acetylene-acetone solution under pressure. Calcium carbide reacts with water to produce acetylene. Old carbide miner's lamps use this reaction to create light. The miner uses a valve to control the drip speed of water and the amount of gas produced which then burns to create light. Industrial processes consume 80 percent of the acetylene produced for chemical synthesis. Welding consumes the remaining 20 percent. Acetylene use is growing due to the demand for more of the gas in production of polyethylene plastics. Phillips Petroleum is working with a new catalyst to increase production efficiency and lower cost of acetylene.