Classification of Chemical Reactions

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Classification of Chemical Reactions

• Notes

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Composition (also called combination or
synthesis)

• Two reactants combine to form one product
• A B ? AB
• Example 3Na P ? Na3P
• Helpful hints
• An element plus another element will always be
  composition if there is only one product, it has
  to be composition
• Note that composition reactions are redox
  reactions

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Decomposition

• One reactant breaks down (decomposes) into two
  (or more) products
• AB ? A B
• Example 2HgO ? 2Hg O2
• Helpful hints
• If there is only one reactant, it has to be
  decomposition
• Note that decomposition reactions are redox

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Single Replacement (Redox)

• An element takes the place of a similar element
  (in terms of charge) in a compound
• A BC ? AC B or
• D BC ? BD C
• Examples 3Na AlCl3 ? 3NaCl Al
• F2 2NaCl ? 2NaF Cl2
• Helpful hints
• An element plus an ionic compound will usually be
  single replacement there are always 2 reactants
  and 2 products

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Single Replacement continued

• Hydrogen is often a participant in redox single
  replacement reactions
• The activity series or a table of standard
  reduction potentials must be used to determine if
  a s.r. redox reaction will occur

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Double Replacement (Ionic)

• The and ions in two ionic compounds switch
  partners
• AB CD ? AD CB
• Example
• 2Na3PO4 3CaCl2 ? Ca3(PO4)2 6NaCl
• Helpful hints
• Two ionic compounds yield two ionic compounds
  remember a ion always goes with a ion and the
  is written first in the formulas

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Combustion

• A hydrocarbon (a compound made up of carbon,
  hydrogen, and sometimes oxygen) reacts with
  oxygen, or burns, to give carbon dioxide plus
  water
• CxHy O2 ? CO2 H2O or
• CxHyOz O2 ? CO2 H2O
• Example CH4 2O2 ? CO2 2H2O
• Helpful hints
• Oxygen is always a reactant and the products are
  always carbon dioxide and water!
• These are also redox reactions