Working out a reactivity series

You can work out a reactivity series for many substances by carrying out displacement reactions. The table below shows the results of reacting different metals with different salt solutions.

Magnesium sulfate solutionCopper(II) sulfate solutionIron(II) sulfate solutionNumber of reactions
MagnesiumNot doneBrown coatingBlack coating2
CopperNo visible reactionNot doneNo visible reaction0
IronBrown coatingNo visible reactionNot done1

Magnesium is the most reactive metal from these three as it undergoes two reactions, iron is next and copper is the least reactive.

Displacement reactions as redox reactions

Here is the balanced ionic equation for the reaction between magnesium and copper(II) sulfate. The equation below shows the ions present on both sides of the equation:

Mg(s) + Cu2+(aq) + SO42-(aq) → Mg2+(aq) + SO42-(aq) + Cu(s)

Sulfate ions, SO42- , appear on both sides of the equation because they do not take part in the reaction. The ionic equation for the reaction is written without sulfate ions:

Mg(s) + Cu2+(aq) → Mg2+(aq) + Cu(s)