Single Replacement Reaction

Single replacement reaction involves the reaction either of a metal with an aqueous solution or a metal with an acid aqueous solution..  It is called replacement reaction since the more active element replaces a less active element from a solution.

1.  Reaction of Metal with an Aqueous solution

     Example:
   

   
In the above equation  Zn metal is added to aqueous silver nitrate solution.  To predict whether reaction is possible or not, activity series of metals   will be used.  Since the position of Zn is higher in the activity series of metal than Ag, it means that Zn is more active than Ag, therefore Zn replaces Ag in the equation forming aqueous zinc nitrate solution.  But if we will have the reverse reaction,

If we do the reverse reaction therefore no reaction will occur, considering that Ag is lower in position in the activity series, meaning Ag is less active than Zn and therefore Ag cannot replace the Zn.

2. Reaction of metal with Aqueous acid solution

     Example:

In the above equation Ni replaced H in the reaction.  Since the location of Ni in the activity series of metal is higher that H, therefore Ni is more active than H and so reaction occurs forming aqueous nickel (II) chloride and hydrogen gas.

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