- Combination Reaction
Reactant A reacts with reactant B forming product C:
A + B --> C
Reactant A and B may be an element or compound, but most of the time they
are elements. Product C is a compound.
Example: Sodium reacts with chlorine to form Sodium chloride.
2Na + Cl2 --> 2NaCl
Another example:Magnesium oxide reacts with water to form Magnesium hydroxide.
MgO + H2O --> Mg(OH)2
- Decomposition Reaction
Reactant AB is broken down into its "subcomponents" A and B.
AB --> A + B
Reactant AB is a compound. A and B may be elements or compounds.
Example: Water, by means of electrolysis, is broken down
into its components hydrogen gas and oxygen gas.
2H2O --> 2H2 + O2
Another Example: Potassium chlorate in the presence of Manganese
oxide (MnO2) acting as a catalyst is heated and broken down into
Potassium chloride and oxygen gas.
2KClO3 --> 2KCl + 3O2
- Replacement Reaction
A in reactant AB is replaced by C forming products AC and B.
AB + C --> AC + B
C can only replace A if and only if C is more
reactive than A. Example: Cupric chloride or Copper (II) chloride
is reacted with zinc forming Zinc chloride and copper metal.
CuCl2 + Zn --> ZnCl2 + Cu
Another example: Magnesium bromide is reacted with copper but there
is no reaction because copper cannot replace magnesium.
MgBr2 + Cu --> NO REACTION
- Double Displacement Reaction
Reactant AC reacts with reactant BD forming products AD and BC.
AC + BD --> AD+ BC
Both AC and BD are compounds (usually ionic).
Example: Strontium nitrate reacts with Aluminum sulfate to
form Strontium sulfate and Aluminum nitrate.
3Sr(NO3)2 + Al2(SO4)3 --> 3SrSO4 + 2Al(NO3)3
Another example:Potassium permanganate reacts with Aluminum
carbonate to form potassium carbonate and Aluminum permanganate.
6KMnO4 + Al2(CO3)3 --> 3K2CO3 + 2Al(MnO4)3
There is another reaction which is called oxidation-reduction reaction (REDOX), but we
will not cover it here. In later discussions we will come to it.