Question

Given the balanced equation representing a reaction:

Fe2O3 + 2Al--> Al2O3 + 2Fe
During this reaction, the oxidation number of Fe changes from
(1) +2 to 0 as electrons are transferred
(2) +2 to 0 as protons are transferred
(3) +3 to 0 as electrons are transferred
(4) +3 to 0 as protons are transferred

Answer 1

Oxidation number of an atom is the charge that atom would have if the compound was composed of ions. Oxidation numbers are positive or negative numbers, but don't confuse them with positive or negative charges on ions or valences.
In this balanced equation, the oxidation number of Fe cation in the reactant is +3 because the valence electrons of Fe is +3. In the product formed, the oxidation number of Fe is 0 since it is a metal and according to its rule the oxidation number of an element in its free (uncombined) state is zero.
Therefore, the oxidation number of Fe changes from +3 to 0 as electrons transferred.

Answer 2

Answer: (3) +3 to 0 as electrons are transferred

Explanation: Oxidation-reduction reaction or redox reaction is defined as the reaction in which oxidation and reduction reactions occur simultaneously.

Oxidation reaction is defined as the reaction in which a substance looses its electrons. The oxidation state of the substance increases.

Reduction reaction is defined as the reaction in which a substance gains electrons. The oxidation state of the substance gets reduced.

For the given reaction:
`Fe_2O_3+2Al\rightarrow Al_2O_3+2Fe`

On reactant side:

Oxidation state of iron = +3

Oxidation state of aluminium = 0

On product side:

Oxidation state of iron = 0

Oxidation state of aluminium = +3

The oxidation state of iron reduces from +3 to 0, it is getting reduced and it undergoes reduction reaction.