Insufficient O2(g) is present, that is, there is excess hydrocarbon present.
O2(g) is the limiting reagent in the reaction.
Reaction products are either CO(g) and/or C(s) and H2O(g).
Hydrocarbon combusts (burns) with a smokey or sooty flame.
Animated Tutorial
Example of Complete Combustion
Methane, CH4(g), a common component of natural gas, combusts in excess oxygen to produce carbon dioxide gas and water vapour.
Write a balanced chemical equation to represent the complete combustion of methane gas.
Write the word equation for the complete combustion of methane:
general equation:
reactants
→
products
word equation:
methane
+
oxygen gas
→
carbon dioxide gas
+
water vapour
Write the formula for each reactant and product in the word equation:
Need to multiply the number of water molecules by 2 to balance the hydrogen atoms.
CH4(g)
+
O2(g)
→
CO2(g)
+
2H2O(g)
No. C atoms :
1
=
1
C atoms balanced
No. H atoms :
4
=
4
H atoms balanced
No. O atoms :
2
≠
2
+
2
O atoms NOT balanced
Need to multiply the number of oxygen molecules by 2 to balance the oxygen atoms.
CH4(g)
+
2O2(g)
→
CO2(g)
+
2H2O(g)
No. C atoms :
1
=
1
C atoms balanced
No. H atoms :
4
=
4
H atoms balanced
No. O atoms :
4
=
2
+
2
O atoms balanced
The balanced chemical equation for the complete combustion of methane gas is:
CH4(g) + 2O2(g) → CO2(g) + 2H2O(g)
Example of Incomplete Combustion
In a particular experiment, excess methane was combusted in limited oxygen to produce soot (solid carbon) and water vapour.
Write a balanced chemical equation to represent the incomplete combustion of methane in this experiment.
Write the word equation for the incomplete combustion of methane:
general equation:
reactants
→
products
word equation:
methane
+
oxygen gas
→
solid carbon
+
water vapour
Write the formula for each reactant and product in the word equation:
to
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