Calcium Carbide (Acetylene) Lab
Preparation of Acetylene and its Combustion
Calcium carbide can be prepared by heating calcium oxide (lime) with
carbon:
This process is called “roasting” and is done is large ovens. Calcium
oxide is a readily available and commonly occurring mineral called lime
and the carbon form used in this reaction is equally available as coal, this
form being called “coke”:

CaO(s) + 3 C (s)  CaC2 (s) + CO(g)
Calcium carbide reacts with water to form acetylene gas: (Write the
reaction)
CaC2 (s) + H2O(l)  C2H2 (g) + CaO(s)
What will the Combustion of Acetylene gas produce? (Write the reaction)
C2H2 (g) + O2 (g)
 CO2 (g) + H2O(l)
In complete combustion will produce side products. What side products
do you think are possible?
Ash: What is ash or soot?
(carbon and carbon products)
What other gases might be produced?
carbon monoxide (CO(g))
water vapor H2O(g)
The following is the edited text of a winning essay, enhanced with diagrams. The bibliography has been excluded.
The Chemistry Hall of Fame is a registered trade mark of York University.
http://www.chem.yorku.ca/hall_of_fame/essays97/acetylene/acetylen.htm
A Winning Essay
Acetylene
by Kelly O'Hara, Collège Notre-Dame, Sudbury
Acetylene was discovered in 1836 in England by E. Davy. Its commercial production was
made in the U.S. by T.L. Wilson.
Acetylene is an odourless, colourless gas produced by a process that uses two abundant and
inexpensive materials: limestone and coal. Calcium carbonate (limestone) is first converted to
calcium oxide, and coal is converted to coke. These two products react producing calcium
carbide, which reacts with water forming acetylene gas, C2H2.
Unlike other hydrocarbons, acetylene can also be produced directly by the reaction of coal and
hydrogen at high temperatures. Many hydrocarbons, including acetylene, can be produced
through oil-based technology, but since oil reserves are diminishing, acetylene may once again
be the raw material for many commercial products.
Acetylene's chemical and physical properties account for many of its uses. Its flame is highly
luminous, thus it was used in miners', bicycle, automobile and street lamps.
Its combustion in pure oxygen produces the highest achievable flame temperature, over 3300
°C, releasing 11,800 J/g, allowing it to weld, cut, braze and solder metals in various
environments: from great depths underwater to the extreme cold of Alaska. The oxy-acetylene
torch is used to repair ships underwater, to construct bridges, pipelines, dams, tunnels,
buildings and to reinforce concrete.
http://www.teachers.yourhomework.com/mrsb/torch.jpg
Acetylene's structure is
The triple bond undergoes addition reactions.
Hydrogen chloride added to acetylene produces vinyl chloride which polymerises forming
polyvinyl chloride used to make pipe, siding, rain gutters, molded bottles, electrical insulation,
floor and wall coverings, upholstery, garden hoses and waterproof clothing.
Hydrogen cyanide added to acetylene produces acrylonitrile used as an intermediate in the
production of nitrile rubbers, acrylic fibers, and insecticides.
Acetic acid added to acetylene forms vinyl acetate used as an intermediate in polymerized
form for films and lacquers.
Alcohol added to acetylene yields vinyl ether used as an anaesthetic.
Water added to acetylene produces acetaldehyde used as a solvent and flavouring in food,
cosmetics and perfumes.
Chlorine adds to acetylene forming 1,2-dichloroethene (DCE) used as a solvent for fats,
phenol and camphor.
Formaldehyde added to acetylene reacts producing 1,4-butynediol which can be hydrogenated
to 1,4-butanediol used as a chain extender for polyurethane. These resins include urethane
foams for cushioning material, carpet underlay and bedding, insulation in refrigerated
appliances and vehicles, sealants, caulking and adhesives.
Acetylene reacts with carbon monoxide and alcohol forming acrylate esters used in the
manufacture of Plexiglass and safety glasses.
Acetylene can polymerize forming polyacetylene. The delocalized electrons of the alternating
single and double bonds between carbon atoms give polyacetylene its conductive properties.
Doping of polyacetylene makes this polymer a better conductor. Polyacetylene is used in
rechargeable batteries that will probably be used in electric cars and may also replace copper
wires in aircraft because of its light weight.
Polydiacetylene is also a polymer of the future. It behaves as a photoconductor and will
probably be used for time-temperature indicators or monitoring of irradiation.
Based on its availability, its many uses and prospective uses, acetylene is definitely special.
Air Composition
The sea-level composition of air (in percent by volume at the
temperature of 15 ° C and the pressure of 101325 Pa) is given
below.
Name
Nitrogen
Symbol
N2
Percent by Volume
78.084 %
Oxygen
O2
20.9476 %
Argon
Ar
0.934 %
Carbon Dioxide
CO2
0.0314 %
Neon
Ne
0.001818 %
Methane
CH4
0.0002 %
Helium
He
0.000524 %
Krypton
Kr
0.000114 %
Hydrogen
H2
0.00005 %
Xenon
Xe
0.0000087 %
Source:
CRC Handbook of Chemistry and Physics
by David R. Lide, Editor-in-Chief
1997 Edition