Aluminium and copper displacement and stoichiometry
hmwadeseo > 06-19-2023, 07:25 AM
This simple demonstration is a display of not only how the reactivity series plays a part in reactions, but also the stoichiometry.
Stoichiometry is derived from the Greek words stoicheion, meaning element, and metrike, meaning measure. It's used to describe the mathematical relationships governing the amounts of materials consumed and produced in a chemical reaction. One of the most important points of stoichiometry is that the quantities of the reactants & products in a chemical reaction are related to each another on a mole basis. The coefficients in a balanced chemical equation give the relative numbers of moles of each reactant and product involved in the reaction.
A solution of copper (II) chloride, CuCl2, is poured over some aluminium foil sitting above a beaker. Nothing happens for a few seconds but all of a sudden, a vigorous, exothermic reaction occurs. The CuClâ‚‚ seemingly eats through the aluminium. Around the outside of the 'hole' and inside the beaker is a pinkish/brown substance. This is elemental copper, Cu. Aluminium displaces copper from its aqueous solution as it is much more reactive in terms of the reactivity series.
From the equation we can see that the stoichiometry is as so: 3 moles aluminium/ 2 moles copper. Cl is a spectator ion in this.
2 Al (s) + 3 CuCl2 (aq) = 2 AICI (aq) + 3 Cu (s)
The reaction initially takes time to start as aluminium naturally forms an oxide layer, Al2O3. The chloride ions in the copper (II) complex disrupt the oxide layer and allow the copper ions to react with the aluminium. The same reaction can be done with copper (II) sulfate, aslong as some sodium chloride is mixed in to the aqueous solution