Write balanced symbol equations to explain the chemistry behind each of the following a.Zinc can be used to protect iron. b.Copper can be plated onto aluminium using copper nitrate solution?

Zinc protects iron because it is more reactive than iron and therefore reacts preferentially with any reagent, for instance oxygen:2Zn + O2 --> 2ZnO

This is called sacrificial protection. If the zinc is completely covering the iron it also protects it physically as there is a coherent layer of zinc oxide on the surface which keeps the metals away from attacking reagents.

If you put clean aluminium into copper nitrate solution you get a displacement reaction:

2Al + 3Cu(NO3)2 --> 2Al(NO3)3 + 3Cu