go to the AUS-e-TUTE homepage
home test Join AUS-e-TUTE game contact
 

 

Combustion of Hydrocarbons

Key Concepts

Complete Combustion of hydrocarbons:

  • Excess O2(g) is present to react.

  • Reaction products are CO2(g) and H2O(g).

  • Hydrocarbon combusts (burns) with a clean flame.

Incomplete Combustion of hydrocarbons:

  • 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.

  1. Write the word equation for the complete combustion of methane:
    general equation: reactants products
    word equation: methane + oxygen gas carbon dioxide gas + water vapour

  2. Write the formula for each reactant and product in the word equation:
    Reactants   Products
    methane :

    oxygen gas :

    CH4(g)

    O2(g)

      carbon dioxide gas :

    water vapour :

    CO2(g)

    H2O(g)

  3. Write the unbalanced chemical equation by substituting the formula for the name of each reactant and product in the word equation:
    word equation : methane + oxygen gas carbon dioxide gas + water vapour
    unbalanced chemical equation : CH4(g) + O2(g) CO2(g) + H2O(g)

  4. Balance the chemical equation:
    unbalanced chemical equation : CH4(g) + O2(g) CO2(g) + H2O(g)
    No. C atoms : 1 = 1 C atoms balanced
    No. H atoms :   4   2 H atoms NOT balanced
    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

  5. 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.

  1. Write the word equation for the incomplete combustion of methane:
    general equation: reactants products
    word equation: methane + oxygen gas solid carbon + water vapour

  2. Write the formula for each reactant and product in the word equation:
    Reactants   Products
    methane :

    oxygen gas :

    CH4(g)

    O2(g)

      solid carbon :

    water vapour :

    C(s)

    H2O(g)

  3. Write the unbalanced chemical equation by substituting the formula for the name of each reactant and product in the word equation:
    word equation : methane + oxygen gas solid carbon + water vapour
    unbalanced chemical equation : CH4(g) + O2(g) C(s) + H2O(g)

  4. Balance the chemical equation:
    unbalanced chemical equation : CH4(g) + O2(g) C(s) + H2O(g)
    No. C atoms : 1 = 1 C atoms balanced
    No. H atoms :   4   2 H atoms NOT balanced
    Need to multiply the number of water molecules by 2 to balance the hydrogen atoms.
    CH4(g) + O2(g) C(s) + 2H2O(g)
    No. C atoms : 1 = 1 C atoms balanced
    No. H atoms :   4 =   4 H atoms balanced
    No. O atoms : 2 =     2 O atoms balanced

  5. The balanced chemical equation for the incomplete combustion of methane gas in this experiment is :
    CH4(g) + O2(g) → C(s) + 2H2O(g)


What would you like to do now?
advertise on the AUS-e-TUTE website and newsletters
 
 

Search this Site

You can search this site using a key term or a concept to find tutorials, tests, exams and learning activities (games).
 

Become an AUS-e-TUTE Member

 

AUS-e-TUTE's Blog

 

Subscribe to our Free Newsletter

Email email us to
subscribe to AUS-e-TUTE's free quarterly newsletter, AUS-e-NEWS.

AUS-e-NEWS quarterly newsletter

AUS-e-NEWS is emailed out in
December, March, June, and September.

 

Ask Chris, the Chemist, a Question

The quickest way to find the definition of a term is to ask Chris, the AUS-e-TUTE Chemist.

Chris can also send you to the relevant
AUS-e-TUTE tutorial topic page.

 
 
 

Share this Page

Bookmark and Share
 
 

© AUS-e-TUTE