1. Combustion Reactions

2. Some Definitions
Combustion is the rapid reaction of a “fuel” in combination with oxygen.
Products are usually an oxide and energy.
Reaction is exothermic.
Hydrocarbons are molecular compounds made up entirely of carbon and hydrogen. They usually are produced from fossil fuels.
Examples:
Methane CH4
Propane C3H8
Octane C8H18

3. The Combustion Triangle
In order for combustion to occur, you need:
The amount of oxygen and the fuel will determine what kind of combustion you have.

4. Complete Combustion
Only occurs when there is a large supply of oxygen.
Only products are energy, water (H2O), and carbon dioxide (CO2).
Fuels will burn cleanly with no sooty residue.
Skeleton equation is CXHY + O2  CO2 + H2O + energy
Flames are blue in colour.

5. Example

6. Incomplete Combustion
Occurs when there is not enough oxygen to convert all carbon to carbon dioxide.
Products are energy, water (H2O), carbon (in the form of soot), carbon monoxide (CO) and carbon dioxide (CO2).
Skeleton equation is CXHY + O2  CO2 + H2O + CO + C + energy
Flames are orange and flicker.

7. Example
incomplete
combustion
complete
combustion

8. Carbon Monoxide

9. Other Combustion Reactions
Elements will also react with oxygen to form oxides.
General word equation: element + oxygen  oxide + energy
General skeleton equation: A + O2  AO + energy
Example: S8 + 8O2  8SO2

10. Other Combustion Reactions
Hydrogen Combustion
2H2 + O2  2H20 + energy
Hydrogen burns cleanly and there is almost an endless supply of water.
Problems:
Hydrogen is highly explosive.
Making hydrogen from water requires energy.

11. Other Combustion Reactions
Phosphorus Combustion
P4 + 5O2  P4O10 + energy
Matches are coated in red phosphorus, which is relatively unreactive.
Friction between the striking strip on a match box and the red phosphorus produces heat energy which converts red phosphorus into white phosphorus (highly reactive).

12. Do Now!
Complete the following skeleton equations. Remember to balance the equations!
A) __Ca (s) + __ O2 (g)  __ ______ (s) + energy
B) __ C3H8 (g) + __ ___ (g)  __ ___ (g) + __ ___ (g) + energy
C) __ C2H4 (g) + __ O2 (g)  __ ___ (g) + __ ___ + energy

13. Do Now!
Complete the following skeleton equations. Remember to balance the equations!
A) 2 Ca (s) + 1 O2 (g)  2 CaO (s) + energy
B) 1 C3H8 (g) + 5 O2 (g)  3 CO2 (g) + 4 H2O (g) + energy
C) 1 C2H4 (g) + 3 O2 (g)  2 CO2 (g) + 2 H2O + energy

14. Homework
Finish worksheets

15. Photo Credits http://www.pc.gc.ca/progs/np-pn/eco/eco5.aspx
combustion