Question

Zinc is more reactive than iron then how is it possible that a layer of zinc can protect bridges from rusting

Answer 1

Iron bridges are coated with zinc. This process is called Galvanization and it is done to prevent rusting (corrosion) of iron. Zinc forms a layer between iron and the atmosphere (with oxygen and water vapour). Zinc is a more electro positive metal, thus it gets oxidized first to zinc oxide, thus saving the iron from getting rusted!!