Topics:

• Combination Rx
• Decomposition Rx
• Single Displacement
• Double Displacement
• Combustion Rx

Next Topic: The Mole Concept

TYPES OF REACTION

i) Combination reactions

A + B → AB  two or more simple substances combine together to produce a more complex substance

Example: 2Mg(s)  +  O₂ (g)  →  2MgO(s)

 ii) Decomposition reactions

AB  →  A  +  B  a compound breaks down to form two or more simpler substances

Examples:  2H₂O(g) → 2H₂(g)  + O₂(g)

                  Cu(OH)₂(s)  →  CuO(s)  +  H₂O(g)

iii) Single displacement reactions

 A   +  BC  →  AB +  C  in this type of reaction one element replaces another element in a compound

 This can be the displacement of one metal by another:

 Zn(s)  +  CuSO₄(aq)  →  Cu(s)  +  ZnSO₄(aq)   
The activity series of metals is used to predict whether  this type of reaction will occur.

 iv) Double Displacement Reactions

 AB  +  CD  →  AD  +  CB these types of reactions always involve ionic compounds, in which the + ion of one compound changes place with the + ion of a second compound.

             NaCl(aq)  +  AgNO₃(aq)  →  NaNO₃(aq)  +  AgCl(s)

             HNO₃(aq)  +  KOH(aq)  →  KNO₃(aq)  +  H₂O(l)

 v) Combustion Reactions 

CH₄ (g)  +  2O₂ (g)  →  CO₂ (g)  +  2H₂O(g)  

in this type of reaction a substance reacts with oxygen producing heat and light;
the products of combustion are usually carbon dioxide and water.

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