Question

When does a single replacement reaction occur?

Answer 1

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:
`"A" + "BC" → "B" + "AC"`
Example: `"Zn" + "CuCl"_2→ "Cu" + "ZnCl"_2`

A halogen replaces another halogen that is in solution:
`"A" + "BC" → "C" + "BA"`
Example: `"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:

`"Mg" + "2HCl" → "H"_2 + "MgCl"_2` (`"Mg"` is above `"H"`)

`"Cl"_2 + "2NaBr" → "Br"_2 + "2NaCl"` (`"Cl"` is above `"Br"`)

`"Cu" + "AlCl"_3→ "no reaction"` (`"Cu"` is below `"Al"`)

The video below summarizes an experiment conducted to compare the activities of three metals (`"Mg, Cu"` and `"Zn"`).