What is the difference between displacement reaction and double displacement reaction ? Give two examples each of these reactions.
Answers
In displacement reaction, one element from its salt is displaced by a more reactive element e.g. in following example, Cu is displaced by Zn from CuSO4 because Zn is more reactive. In double displacement reaction, exchange of ions takes place between two reactants to form new products.
Displacement vs Double Displacement Reaction
Displacement reactions occur in the presence of a reactive chemical species. A very reactive chemical species can replace an anion or a cation of a compound. This displacement occurs according to the reactivity series. The reactivity series is a list of elements that shows the order of the reactivity of those elements from most reactive elements to the least reactive elements. Therefore, it gives an idea about the capability of an element to displace another element. This displacement can occur as a single displacement or a double displacement. The main difference between displacement and double displacement reaction is that in displacement reaction, a single chemical species is replaced whereas, in double displacement reactions, two chemical species are replaced.
Key Areas Covered
1. What is Displacement Reaction
– Definition, Properties, Examples
2. What is Double Displacement Reaction
– Definition, Properties, Examples
3. What is the Difference Between Displacement and Double Displacement Reaction
– Comparison of Key Differences
Key Terms: Acid-Base Reactions, Alkylation, Displacement Reaction, Double Displacement Reaction, Neutralization, Precipitation, Reactivity Series
Difference Between Displacement and Double Displacement - Comparison Summary
What is a Displacement Reaction
A displacement reaction is a chemical reaction that occurs by replacing a chemical species in a molecule by another chemical species. Displacement reactions take place in the presence of a more reactive species which has a high binding affinity for a cation or an anion present in a compound. The reactive species can be a metal element, anion or a cation. The general form of a displacement reaction can be given as below.
A-B + C → A-C + B
In the above reaction, B in the A-B molecule has been replaced by C. Therefore, C is a highly reactive chemical species than B. In order to complete the displacement reaction, A should have binding affinity for both B and C. B and C can be a metal element, anion or a cation.
The elements that are displaced can be predicted by looking at the reactivity series. The reactivity series is a list of elements that is categorized in the order of their reactivity from the most reactive element to the least reactive element. Therefore, elements in the upper part of that list are highly reactive than the elements in the lower part of the list. Then the elements that are in the lower part can be replaced by the elements in the upper part easily.
Zn(s) + 2HCl(aq) → ZnCl2(aq) + H2(g)
The above reaction shows the displacement of H+ cation by Zn metal. Here the Zn is bonded to Cl– anion.
The displacement reactions are used commonly in displacing halogens from compounds. The order of halogens in the reactivity series is F>Cl>Br>I. This means the highest reactivity is shown by Fluorine whereas the lowest reactivity is shown by iodine. Therefore, if we need to obtain Br2 liquid out of NaBr solution, we can bubble Cl2(g) and use a separation method to separate bromine liquid. The reaction is given below.
NaBr(aq) + Cl2(g) → NaCl(aq) + Br2(aq)