Answer – Examples of single replacement reactions:

$\mathbf{Zn}\mathbf{ + }\mathbf{2}\mathbf{HCl}\mathbf{ \to }{\mathbf{ZnCl}}_{\mathbf{2}}\mathbf{ + }{\mathbf{H}}_{\mathbf{2}}$

$\mathbf{2}\mathbf{Al}\mathbf{ + }\mathbf{3}{\mathbf{CuCl}}_{\mathbf{2}}\mathbf{ \to }\mathbf{2}{\mathbf{AlCl}}_{\mathbf{3}}\mathbf{ + }\mathbf{3}\mathbf{Cu}$

${\mathbf{Cl}}_{\mathbf{2}}\mathbf{ + }\mathbf{2}\mathbf{NaBr}\mathbf{ \to }\mathbf{2}\mathbf{NaCl}\mathbf{ +}{\mathbf{Br}}_{\mathbf{2}}$

${\mathbf{FeSO}}_{\mathbf{4}}\mathbf{ + }\mathbf{Pb}\mathbf{ \to }{\mathbf{PbSO}}_{\mathbf{4}}\mathbf{ + }\mathbf{Fe}$

The first two equations represent cation replacement reactions, where one cation replaces another. The third and fourth equations, on the other hand, represent anion replacement reactions, where one anion replaces another.

Explanation:

A single replacement reaction is one in which a single element replaces another element in a compound. Also known as a single displacement reaction, it usually involves a more reactive element replacing a less reactive one. Such a reaction can be indicated by the below equation:

$\mathrm{X} + \mathrm{YZ} \to \mathrm{XY} + \mathrm{Z}$

Element Z in the aqueous compound YZ is replaced by the element X to form the new compound XY.

Generally, single replacement reactions tend to be exothermic and result in the release of heat or light energy.

Here are a few examples of single replacement reactions:

$\mathrm{Zn} + 2\mathrm{HCl} \to {\mathrm{ZnCl}}_2 + {\mathrm{H}}_2$

$2\mathrm{Al} + 3{\mathrm{CuCl}}_2 \to 2{\mathrm{AlCl}}_3 + 3\mathrm{Cu}$

These are examples of cation replacement reactions, where one cation (Zn) replaces another cation (H).

Conversely, the two reactions below are examples of anion replacement reactions, where one anion (Cl) replaces another anion (Br).

${\mathrm{Cl}}_2 + 2\mathrm{NaBr} \to 2\mathrm{NaCl} +{\mathrm{Br}}_2$

${\mathrm{FeSO}}_4 + \mathrm{Pb} \to {\mathrm{PbSO}}_4 + \mathrm{Fe}$

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