Which of the following reactions would be classed as redox reactions? Explain why this isCorrosion of iron to iron (III) oxide (Fe2O3) and burning of magnesium in air

Expert Answers
swatisakk eNotes educator| Certified Educator

Burning of Magnesium in air is a Redox reaction. Red-ox reaction is a reaction in which one of the elements/compounds loses electrons and the other gains electrons.

In case of Magnesium, it reacts with oxygen to lose 2 electrons to form Mg2+ and Oxygen gains 4 electrons to form 2O2-

The reaction is:

2Mg + O2 -> 2[Mg2+] [O2-]

llltkl | Student

In fact both of them are examples of redox reactions.

Burning of magnesium: 2Mg + O2 -----> 2MgO

Here, oxidation number of Mg changes from 0 to +2 and that of oxygen changes from 0 to -2. So this is definitely a redox reaction. 

Corrosion of iron to iron (III) oxide:4Fe + 3O2 -----> 2Fe2O3

Here, oxidation number of Fe changes from 0 to +3 and that of oxygen changes from 0 to -2. So this is also a redox reaction. Also please see the comments and other reactions associated with rusting in the given link.