The Reactivity Series

Ionic Equations.

The displacement reactions can be written as ionic equations.
In the example using iron and copper(II) sulfate (see previous page)

iron  +  copper(II) sulfate   arrow    iron sulfate   +  copper.
Fe(s)    +     CuSO4(aq)      arrow       FeSO4(aq)    +    Cu(s)

Copper(II) sulfate and iron sulfate are ionic compounds.
When they are dissolved in water
 the ions become separated by the water molecules.

If we write the equation showing the ions we have

Fe(s)  +  Cu2+(aq) +  SO42-(aq) arrow   Fe2+(aq)  +  SO42-(aq)  +  Cu(s)

In going from reactants to products
iron metal - Fe(s)  has become iron ions - Fe2+(aq)
 copper ions - Cu2+(aq)  have become copper metal -  Cu(s)
 sulfate ions - SO42-(aq) are not changed during the reaction.
Sulfate ions are the same on the left and the right side of the arrow.
Ions which do not change during the reaction are called spectator ions.

Spectator ions can be left out of the equation, giving

Fe(s)  +  Cu2+(aq)   arrow   Fe2+(aq)  +  Cu(s)

This is the ionic equation
 for the reaction between iron and copper(II) sulfate.
Iron is oxidised and copper is reduced.

Similarly, the reaction between tin and lead chloride may be written as

Sn(s)   +   Pb2+(aq)    arrow         Sn2+(aq)   +   Pb(s)

Tin is oxidised and lead is reduced.

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