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Wize University Chemistry Textbook > Chemical Reactions

Classifying Reaction Types

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Combustion Reactions


Combustion reaction: a reaction where a compound reacts with oxygen to produce the oxides of the elements that make up the compound

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Complete vs Incomplete Combustion:

Complete Combustion: when an excess of oxygen reacts with a hydrocarbon to produce CO2 + H2O. This reaction releases energy.

Hydrocarbon + O2 → CO2 + H2O + energy

Example:
Balance the following equation:
1
C3H8(g) +
5
O2(g) →
3
CO2(g) +
4
H2O(g)


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Incomplete Combustion: when there is insufficient oxygen present and the oxygen reacts with a hydrocarbon to form CO2 + CO + H2O + C. Here, the elements in the fuel don't combine with oxygen to the greatest extent possible.



Note: you can't balance incomplete combustion reactions :)
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Classifying Reactions

The following are the options for classifying reactions:

  • Combination
  • Decomposition
  • Single displacement/replacement
  • Double displacement/replacement aka metathesis
  • Combustion

1) H2SO4     +    Fe      -->        H2    +   FeSO4

ans:
single displacement reaction

2) C12H22O11 + O2 --> CO2 + H2O

ans:
combustion reaction

3) Zn + S -- > ZnS

ans:
combination reaction

4) Mg(OH)2   +   H2SO4      -->        MgSO4    +    H2O

ans:
double displacement reaction

5) NH4NO3   -->     N2O   +   H2O

ans:
decomposition reaction

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Example: Balancing

Balance the following reaction:

What type of reaction is this?
combustion

C5H10O(l)+O2(g)→ CO2(g)+H2O(l)\text{C}_5H_{10}\text{O}_{\left(l\right)}+\text{O}_{2\left(g\right)}\rightarrow\ \text{CO}_{2\left(g\right)}+\text{H}_2\text{O}_{\left(l\right)}

C5H10O(l)+7 O2(g)→ 5 CO2(g)+5 H2O(l)C_5H_{10}O_{\left(l\right)}+7\ O_{2\left(g\right)}\rightarrow\ 5\ CO_{2\left(g\right)}+5\ H_2O_{\left(l\right)}
Wize Tip
When balancing combustion reactions, if you ever end up with fractions, multiply by the largest common denominator to get whole number coefficients.