Reaction of Magnesium with Carbon Dioxide Magnesium metal burns in an atmosphere of carbon dioxide producing light and a black residue

Purpose n To observe a combustion reaction which does not require oxygen n To understand oxygen transfer from a covalent compound to a metal to form an ionic compound

Demonstration n Once activation energy was supplied, magnesium continued to burn in a tank filled with carbon dioxide n A black substance was produced

Concepts 1.Relative Stability 2.Combustion Reactions 3.Single Replacement Reactions

1.Relative Stability n Substances may be extremely unreactive under one set of conditions and extremely reactive under others n All substances have different reactivity characteristics relative to others n Mg is stable as the element yet when it reacts it reacts violently with evolution of much heat and light

2.Combustion Reactions n A combustion reaction is a reaction that liberates heat and light n Magnesium undergoes combustion under very different (dissimilar) conditions u air with both oxygen and nitrogen F air will support life u carbon dioxide F carbon dioxide will not support life n Magnesium is so reactive it does not distinguish between the two conditions but reacts under both

3.Single Replacement Reactions n A single replacement reaction is of the form u A + BCB + AC n When such a reaction occurs it must be concluded that A is more reactive than B toward u A takes B away from C u We say that A has “replaced” B

Conclusions n The magnesium burned in a carbon dioxide atmosphere without oxygen n The reason the magnesium burned was because it combined with the oxygen in the carbon dioxide leaving elemental carbon behind n Thus, magnesium was more reactive than carbon toward oxygen

Comments n The combustion reaction is represented by the following chemical equation 2Mg + CO 2 2MgO + C n The magnesium has been oxidized and the carbon in carbon dioxide has been reduced to elemental carbon