Metals and Metallurgy - SS2 Chemistry Past Questions and Answers - page 5

Displacement reactions of metals can be influenced by several factors, including concentration and competition between metals for available ions. These factors affect the likelihood and extent of a displacement reaction.

●     Concentration: The concentration of metal ions in the solution can impact the displacement reaction. Higher concentrations of metal ions increase the likelihood of a displacement reaction occurring. This is because a higher concentration provides more opportunities for the more reactive metal to come into contact with the metal ions and replace the less reactive metal. However, excessively high concentrations can reach a point where the solution becomes saturated, reducing the rate of reaction.

●     Competition: When multiple metals are present and capable of displacing each other from a solution, competition for available ions becomes a factor. The more reactive metal has a higher tendency to displace the less reactive metal. If two metals have similar reactivity, the one with a higher concentration or a stronger driving force (e.g., greater electrochemical potential) will have a higher probability of displacing the other.

For example, consider the reaction between zinc (Zn) and iron (Fe) ions in a solution of iron(II) sulphate (FeSO4):

Zn(s) + FeSO4(aq) → ZnSO4(aq) + Fe(s)

In this case, zinc, being more reactive, displaces iron from the iron sulphate solution, leading to the formation of zinc sulphate and iron metal.

However, if the concentration of zinc ions is insufficient or the concentration of iron ions is too high, the reaction may not occur. The competition between zinc and iron for the available iron ions affects the displacement reaction's outcome.