Combination reactions: When two or more elements or compounds combine to form one compound


Eg. Forming of sodium chloride


2Na(s) + Cl2(g) => 2NaCl(s)

Decomposition reactions: When one compound decomposes to form 2 or more simpler substances


eg. Electrolysis


2H2O => 2H2(g) + O2(g)

2NaCl(s) => 2Na(s) + Cl2(g)

Combustion reactions: An exothermic reaction with rapid oxidation and possible emission of light, must have O2 as a reactant


Eg. burning of coal (Combustion of all substances containing carbon produces carbon dioxide)


C(g)+O2(g) => CO2(g)

Eg. burning of fuel (Combustion of all substances containing hydrogen produces water)



CH4(g) + 2O2(g) → CO2(g) + 2H2O(l)

Combustion of all substances containing sulfur produces sulfur dioxide.






Single Displacement reactions: When atoms of one element in a compound are displaced (or replaced) by atoms from a pure element


Eg. A more reactive metal added to a metal compound


Zn(s) + CuSO4(aq) => ZnSO4(aq) + Cu(s)

As the zinc metal loses electrons in the reaction, it's oxidation number has changed and has been oxidized, while copper has gained electrons, changing its oxidation number too.