# The Reaction Between Magnesium and CO₂


## Chemical Concepts Demonstrated

• Active metal chemistry
• The limited usefulness of CO2 fire extinguishers

## Demonstration

 A slab of dry ice is cut in half and a small "crater" is melted into one of the pieces. An ignited magnesium strip is placed in the "crater", and the other half of the dry ice is placed on top.

## Observations

The magnesium strip burns brightly in the air, but continues to burn in the carbon dioxide environment.

## Explanations (including important chemical equations)

This reaction is a combustion and oxidation. What's unusual, however, is that magnesium is reactive enough to be combusted and oxidized in a reaction with carbon dioxide:

$\ce{2 Mg + CO2 -> 2 MgO + C}$

Under normal combustion/oxidation circumstances, oxygen is the reactant.

Carbon dioxide fire extinguishers work by smothering a fire in carbon dioxide. This is only an effective means of extinguishing a fire if carbon dioxide itself cannot be used as a fuel source.

## Contributors

The Reaction Between Magnesium and CO₂ is shared under a not declared license and was authored, remixed, and/or curated by LibreTexts.