Write the ionic equation for the displacement reaction, by adding the half equation. Magnesium+copper(2) sulfate--> magnesium sulfate+ copper
In this reaction `Cu^(2+)` ions will be displaced by `Mg` and in the final solution we will get` Mg^(2+)` ions and `Cu` precipitate. `SO_4^(2-) ` ions in `CuSO_4` will be act as spectator ion which will not take part in the reaction.
`Mg_((s)) rarr Mg^(2+)_(aq)+2e ----(1)`
`Cu^(2+)_(aq)+2e rarr Cu_((s)) ----(2)`
(1)+(2) will give the answer.