(a) What is a reactivity series of elements? How is it developed? Arrange the following elements as they are arranged in the reactivity series: Aluminum, Calcium, Copper, Lead

(b) Write balanced chemical equation to show the reaction of iron (III) oxide ($\mathrm{Fe_2O_3}$) with aluminium.

(a) The reactivity series is a list of metals arranged in the order of their decreasing activities. It is developed by performing displacement experiments. The correct order of the given elements in the reactivity series is: Calcium, Aluminium, Iron, Copper, Lead

(b) The balanced chemical equation for the reaction of iron (III) oxide (Fe2O3) with aluminium is: 2Al + Fe2O3 $\rightarrow$ Al2O3 + 2Fe