IC6.5.5 Displacement reactions © Oxford University Press Displacement reactions

IC6.5.5 Displacement reactions © Oxford University Press When a strip of zinc foil is dipped into copper(II) sulfate solution, it becomes coated in copper and the blue colour of the solution gradually fades.

IC6.5.5 Displacement reactions © Oxford University Press zinc + copper(II) sulfate  zinc sulfate + copper This type of redox reaction called a displacement reaction. The temperature rises because it is an exothermic reaction.

IC6.5.5 Displacement reactions © Oxford University Press One way of understanding displacement reactions involves the reactivity series of metals. A more reactive metal can displace a less reactive metal from its compounds.

IC6.5.5 Displacement reactions © Oxford University Press Zinc is more reactive than copper, so it displaces or pushes out copper from copper(II) sulfate. The sulfate swaps from the less reactive metal to the more reactive one.

IC6.5.5 Displacement reactions © Oxford University Press Will a displacement reaction happen between magnesium and tin chloride solution? Explain.  Yes. Magnesium is more reactive than tin and so it displaces tin from tin chloride. Magnesium chloride and tin are produced.

IC6.5.5 Displacement reactions © Oxford University Press Displacement reactions can also be explained in terms of redox reactions involving electrons. Look at the reaction between zinc and copper(II) sulfate solution: Zn(s) + CuSO 4 (aq)  ZnSO 4 (aq) + Cu(s)

IC6.5.5 Displacement reactions © Oxford University Press The sulfate ions act as spectator ions. You can write two half equations: Zn(s) – 2e –  Zn 2+ (aq) Zinc atoms are oxidised. Cu 2+ (aq) + 2e –  Cu(s) Copper(II) ions are reduced.

IC6.5.5 Displacement reactions © Oxford University Press Now answer these questions about the reaction between magnesium and tin chloride solution. 1.What is the balanced symbol equation for the reaction?  Mg + SnCl 2  MgCl 2 + Sn

IC6.5.5 Displacement reactions © Oxford University Press Mg + SnCl 2  MgCl 2 + Sn 2.Explain which reactant is reduced and which reactant is oxidised.  Magnesium is oxidised (it loses electrons) and tin ions are reduced (they gain electrons).