Classifications of Chemical Equations

  1. Simple Composition (Addition reaction) – sc
  • Element + element  compoundA + B C
  • 2 Na + Cl2 2 NaCl
  1. Simple Decomposition (breaks down into elements) – sd
  • Compound  element + elementAB  A + B
  • 2 H2O  2 H2 + O2
  1. Single Replacement – sr
  • Element + compound  element + compoundA + BC  AC + B
  • Mg + 2 NaBr  MgBr2 + 2 Na
  • “Positive to opposite negative” is a key phrase for this type and for double replacement
  1. Double Replacement – dr
  • Compound A + compound B  compound C + compound D
  • 6 NaCl + Al2(CO3)3 3 Na2CO3 + 2 AlCl3
  • Think of these two replacement reactions as a square dance, where the metals (males) switch partners to the other nonmetals (females).
  1. Hydrocarbon Combustion – hc
  • ___ CxHy + ___ O2 ___ CO2 + ___ H2O
  • A hydrocarbon is a natural fuel that is composed only of carbon and hydrogen. It always burns in the presence of oxygen to produce carbon dioxide and water vapour.
  • To balance, it is easier to deal with the hydrogen first, then the carbon, and finally the oxygen – keeping in mind that there is oxygen on both sides.
  • C3H8 + 5 O2 3 CO2 + 4 H20
  • If the number of hydrogen is odd when divided by two, so that the water has an odd number in front of it, double the coefficient in front of the hydrocarbon.
  • 2 C4H10 + 13 O2 8 CO2 + 10 H2O
  1. Other – a reaction that doesn’t fit any of the above types.

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