Question

Define the term chemical displacement reaction. Support your answer with two examples and write fully balanced chemical equations.

Answer 1

Displacement reaction: A displacement reaction is a type of chemical reaction in which a more reactive metal displaces a less reactive metal from its salt solution.

Example of displacement reaction:

1. Displacement of Copper (Cu) by Iron (Fe) in the chemical reaction shown below:

$\mathrm{Fe}\left(\mathrm{s}\right)+{\mathrm{CuSO}}_4\left(\mathrm{aq}\right)\to {\mathrm{FeSO}}_4\left(\mathrm{aq}\right)+\mathrm{Cu}\left(\mathrm{s}\right)$

(Iron) (Copper sulfate) (Ferrous sulfate) (Copper)

• Balancing any reaction equation means the same number of atoms of each element on the left side of the arrow as on the right.

Element	Reactant side	Product side
1. Fe	1	1
2. Cu	1	1
3. S	1	1
4. O	4	4

Hence, the equation is already balanced, so no changes are required.

• Iron is more reactive than Copper as it lies above Copper in the reactivity series.
• Therefore, it displaces Copper from its salt solution i.e. Copper sulfate to form Iron sulfate and Copper.

2. Displacement of Silver (Ag) by Copper(Cu) in the chemical reaction shown below:

$$\begin{gathered} \mathrm{Cu}+{\mathrm{AgNO}}_3⟶\mathrm{Cu}{\left({\mathrm{NO}}_3\right)}_2+\mathrm{Ag} \\ \left(\mathrm{copper}\right)(\mathrm{silver}\mathrm{nitrate})(\mathrm{copper}\mathrm{nitrate})\left(\mathrm{silver}\right) \end{gathered}$$

Element	Reactant side	Product side
1. Ag	1	1
2. Cu	1	1
3. N	1	2
4. O	3	6

• Balancing any reaction equation means the same number of atoms of each element on the left side of the arrow as on the right.
• Hence, after balancing;

$$\begin{gathered} \mathrm{Cu}+2{\mathrm{AgNO}}_3⟶\mathrm{Cu}{\left({\mathrm{NO}}_3\right)}_2+2\mathrm{Ag} \\ \left(\mathrm{copper}\right)(\mathrm{silver}\mathrm{nitrate})(\mathrm{copper}\mathrm{nitrate})\left(\mathrm{silver}\right) \end{gathered}$$

Element	Reactant side	Product side
1. Ag	2	2
2. Cu	1	1
3. N	2	2
4. O	6	6

• Copper is more reactive than silver as it lies above silver in the reactivity series.
• Therefore, it displaces Silver from its salt solution i.e.silver nitrate to form copper sulfate and silver.
• Hence, the final equation will be-

$$\begin{gathered} \mathrm{Cu}\left(\mathrm{aq}\right)+2{\mathrm{AgNO}}_3\left(\mathrm{aq}\right)⟶\mathrm{Cu}{\left({\mathrm{NO}}_3\right)}_2\left(\mathrm{aq}\right)+2\mathrm{Ag}\left(\mathrm{aq}\right) \\ \left(\mathrm{copper}\right)(\mathrm{silver}\mathrm{nitrate})(\mathrm{copper}\mathrm{nitrate})\left(\mathrm{silver}\right) \end{gathered}$$