When does a single replacement reaction occur?

Jan 25, 2014

A single replacement reaction occurs when an element reacts with a compound to produce a new element and a new compound.

Explanation:

A single replacement reaction occurs when an element reacts with a compound to produce a new element and a new compound.

There are two types of single replacement reactions:

A metal replaces another metal that is in solution:
$\text{A" + "BC" → "B" + "AC}$
Example: ${\text{Zn" + "CuCl"_2→ "Cu" + "ZnCl}}_{2}$

A halogen replaces another halogen that is in solution:
$\text{A" + "BC" → "C" + "BA}$
Example: $\text{Br"_2 + "2KI" → "I"_2+ "2KBr}$

To determine whether a given single replacement will occur, you must use an “Activity Series” table.

If the metal or the halogen is above the element it will replace based on the activity series, a single displacement reaction will occur.

Examples:

${\text{Mg" + "2HCl" → "H"_2 + "MgCl}}_{2}$ ($\text{Mg}$ is above $\text{H}$)

$\text{Cl"_2 + "2NaBr" → "Br"_2 + "2NaCl}$ ($\text{Cl}$ is above $\text{Br}$)

$\text{Cu" + "AlCl"_3→ "no reaction}$ ($\text{Cu}$ is below $\text{Al}$)

The video below summarizes an experiment conducted to compare the activities of three metals ($\text{Mg, Cu}$ and $\text{Zn}$).