Question

Given the balanced equation representing a reaction:
2Fe + 3Cu2+ ==>2Fe3+ + 3Cu
When the iron atoms lose six moles of electrons, how many moles of electrons are gained by the copper ions?
(1) 12 moles (3) 3 moles
(2) 2 moles (4) 6 moles

Answer 1

(4) 6 moles of electrons are gained, there is no change.

Answer 2

Answer : The correct option is, (4) 6 moles

Explanation :

Oxidation-reduction reaction : It is defined as the reaction in which the oxidation and reduction reaction takes place simultaneously.

Oxidation reaction : It is defined as the reaction in which a substance looses its electrons. In this, oxidation state of an element increases. Or we can say that in oxidation, the loss of electrons takes place.

Reduction reaction : It is defined as the reaction in which a substance gains electrons. In this, oxidation state of an element decreases. Or we can say that in reduction, the gain of electrons takes place.

The given balanced chemical reaction is :

$2Fe+3Cu^{2+}\rightarrow 2Fe^{3+}+3Cu$

The oxidation-reduction half reaction will be :

Oxidation : $Fe\rightarrow Fe^{3+}+3e^-$        .................(1)

Reduction : $Cu^{2+}+2e^-\rightarrow Cu$     ..................(2)

In this reaction, the oxidation state of 'Fe' changes from (0) to (+3) that means Fe lost 3 electrons and it shows oxidation and the oxidation state of 'Cu' changes from (+2) to (0) that means Cu gains 2 electrons and it shows reduction.

From the balanced chemical reaction we conclude that the electrons are not balanced. Now, first balance the electrons.

In order to balance the electrons, multiplying the equation 1 by 2 and equation 2 by 3, we get :

$2Fe\rightarrow 2Fe^{3+}+6e^-$

$3Cu^{2+}+6e^-\rightarrow 3Cu$

That means the number of moles of electrons are loses by the iron are 6 and the number of moles of electrons are gained by the copper ions are 6.

Therefore, the correct option is, (4) 6 moles