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The percentage yield shows how much product is obtained compared to the maximum possible mass. The atom economy of a reaction gives the percentage of atoms in reactants that form a desired product.

Calculations involving the mole can be used to determine unknown concentrations, volumes and masses in reactions. One mole of any gas occupies 24 dm3 at room temperature and pressure.

The greater the frequency of successful collisions between reactant particles, the greater the reaction rate. Temperature, concentration, pressure and the use of catalysts affect reaction rate.

Chemical reactions are reversible and may reach a dynamic equilibrium. The direction of some reversible reactions is altered by changing the reaction conditions.

Understanding how to approach exam questions helps to boost exam performance. Question types will include multiple choice, structured, mathematical and practical questions.