The atom economy (atom utilisation) is a measure of the amount of starting materials that end up as useful products. It is important for sustainable development and for economic reasons to use reactions with high atom economy. The percentage atom economy of a reaction is calculated using the balanced equation for the reaction as follows: Relative formula mass of desired product from equation Sum of relative formula masses of all reactants from equation × 100 Students should be able to: • calculate the atom economy of a reaction to form a desired product from the balanced equation