Magnesium metal burns in air producing intenselight

Magnesium Burning

Demonstration The reaction was initiated in a

flame

The reaction produced intense light

The magnesium reacted with the oxygen and nitrogen in the atmosphere to form solid products

Purpose To observe a metal while it burns

Concepts

1. Combustion Reactions

2. Combination Reactions

3. Energy

1. Combustion Reactions “Burning” reactions Usually organic substances

wood paper

By definition a combustion reaction is the exothermic reaction of a substance, usually with oxygen (but not always)

Light typically is also a product of the reaction

Metals also burn!

2. Combination Reactions General form

A + B C

In this demonstration 2 Mg + O2 MgO

3 Mg + N2 Mg3N2

The oxygen and nitrogen occur

naturally in the atmosphere O2 is 21% of air N2 is 78% of air

3. Energy Two types of energy are produced in this

demonstration heat energy Hf MgO = -601.83

kJ/mole (kiloJoules per mole) this is said to be the ‘heat of

formation’ for MgO the negative sign indicates the

formation is exothermic

light energy approximately 10% of the energy of

combustion occurs as light in this demonstration

more light than any other known reaction

Conclusions When the energy of activation was

applied magnesium burst into flame

Magnesium burned with the intense production of light and heat

The reaction was a combination reaction which used gaseous components from the atmosphere

Comments This is a redox reaction in addition to a

combination and combustion reaction

Mg begins as oxidation number 0 In both magnesium oxide and

magnesium nitride the oxidation number of magnesium is 2+

magnesium has lost electrons therefore has been oxidized

Flashbulbs contain magnesium filaments