Metals and Equilibria: Displacement Reactions

Metals and Equilibria: Displacement Reactions

  • Displacement reactions involve a more reactive metal displacing a less reactive metal from its compound. It’s a type of redox reaction where both oxidation and reduction occur.

  • The reactivity series of metals ranks metals according to how readily they participate in displacement reactions. The series, from most to least reactive, is Potassium, Sodium, Calcium, Magnesium, Aluminium, Zinc, Iron, Tin, Lead, (Hydrogen), Copper, Silver, Gold.

  • In a displacement reaction, the more reactive metal ends up as a part of the compound, and the less reactive metal is displaced or removed.

  • You can predict whether a displacement reaction will occur or not by looking at the reactivity series. If Metal A is higher in the reactivity series than Metal B, then Metal A will displace Metal B from its compound.

  • In these reactions, the more reactive metal is oxidised (loses electrons) and the less reactive metal or metal ion is reduced (gains electrons).

  • An example of a displacement reaction is when zinc displaces copper from copper sulphate to form zinc sulphate and copper: Zn + CuSO4 -> ZnSO4 + Cu.

  • Real-world applications of displacement reactions include extracting a metal from its ore, galvanising iron and in electrochemical cells.

  • Displacement reactions are exothermic, which means they release energy in the form of heat.

  • The applications of displacement reactions are many: in the purification of metals, treatment of water, and metal extraction to cite a few.

  • Remember, in any reaction equilibrium the rate of the forward reaction equals the rate of the reverse reaction. In displacement reactions, this equilibrium can be shifted by changing conditions such as concentration, pressure, or temperature.

  • Le Chatelier’s principle can predict the effect of changes in conditions on the position of the equilibrium in a reaction. For displacement reactions, an increase in the concentration of reactants or decrease in the concentration of products would favour the forward reaction, leading to an increased yield of the product.

  • Another way to shift the equilibrium is by changing the temperature. For exothermic reactions, increasing the temperature will move the equilibrium to the left (opposite the heat term), favouring the backward reaction. For endothermic reactions, increasing the temperature will move the equilibrium to the right (same side as the heat term), favouring the forward reaction.