Question

In a ___ reaction a more active element displaces a less active element (displacement/ decomposition).

Answer 1

1. Displacement reaction

A displacement reaction is a reaction in which a more reactive element displaces a less reactive element from its compound. The displacement occurs in accordance with the reactivity series. It is represented as:

$\mathrm{A}+\mathrm{BC}\to \mathrm{AC}+\mathrm{B}$. Here, A is more reactive than B.

An example of a displacement reaction is given below:

$$\begin{gathered} \mathrm{Fe}\left(\mathrm{s}\right)+{\mathrm{CuSO}}_4\left(\mathrm{aq}\right)\to \mathrm{Fe}\left({\mathrm{SO}}_4\right)\left(\mathrm{aq}\right)+\mathrm{Cu}\left(\mathrm{s}\right) \\ \left(\mathrm{Iron}\right)(\mathrm{Copper}(\mathrm{Ferrous}\left(\mathrm{Copper}\right) \\ \mathrm{sulphate})\mathrm{sulphate}) \end{gathered}$$

2. Decomposition reaction

A decomposition reaction is a reaction in which a compound decomposes to form simpler products. It is represented as:

$\mathrm{AB}\to \mathrm{A}+\mathrm{B}$. Here, AB is the reactant.

An example of a decomposition reaction is given below:

$$\begin{gathered} 2{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)\to 2{\mathrm{H}}_2\left(\mathrm{g}\right)+{\mathrm{O}}_2\left(\mathrm{g}\right) \\ \left(\mathrm{Water}\right)\left(\mathrm{Hydrogen}\right)\left(\mathrm{Oxygen}\right) \end{gathered}$$

So, in a displacement reaction, a more active element displaces a less active element.