Question

Onsider a galvanic cell in which al3 is reduced to elemental aluminum, and magnesium metal is oxidized to mg2 . write the balanced half-cell reactions that take place at the cathode and at the anode.

Answer 1

Two Half Cell reactions are as follow,

                                    3e⁻  +    Al⁺³    →  Al            (Reduction Reaction)

                                    Mg   →   Mg⁺²  +  2e⁻           (Oxidation Reaction)

In order to balance the number of electrons, multiply reduction reaction by 2 and oxidation reaction by 3.
So,
                                    6e⁻  +    2 Al⁺³    →  2 Al           

                                    3 Mg   →   3 Mg⁺²  +  6e⁻           (e⁻ cancelled)
                                _______________________

                               2 Al⁺³ + 3 Mg  →  2 Al  +  3 Mg⁺²

Result:
            At Anode Magnesium metal is Oxidized and At Cathode Aluminium Ions are reduced.

Answer 2

The balanced reduction half-cell reaction at cathode is $\boxed{{\text{A}}{{\text{l}}^{3+}}+3{e^-}\to{\text{Al}}}$  

The balanced oxidation half-cell reaction at anode is $\boxed{{\text{Mg}}\to{\text{M}}{{\text{g}}^{2+}}+2{e^-}}$  

Further Explanation:

Redox reaction:

Redox is a term that is used collectively for the reduction-oxidation reaction. It is a type of chemical reaction in which the oxidation states of atoms are changed. In this reaction, both reduction and oxidation are carried out simultaneously. Such reactions are characterized by the transfer of electrons between the species involved in the reaction.

The process of gain of electrons or the decrease in the oxidation state of the atom is called reduction while that of loss of electrons or the increase in the oxidation number is known as oxidation. In redox reactions, one species lose electrons and the other species gain electrons. The species that lose electrons and itself gets oxidized is called as a reductant or reducing agent. The species that gains electrons and gets reduced is known as an oxidant or oxidizing agent. The presence of a redox pair or redox couple is a must for the redox reaction.

The general representation of a redox reaction is,

${\text{X}}+{\text{Y}}\to{{\text{X}}^+}+{{\text{Y}}^-}$

The oxidation half-reaction can be written as:

${\text{X}}\to{{\text{X}}^+}+{e^-}$

The reduction half-reaction can be written as:

${\text{Y}}+{e^-}\to{{\text{Y}}^-}$

Here, X is getting oxidized and its oxidation state changes from $0$ to +1 whereas B is getting reduced and its oxidation state changes from 0 to -1. Hence, X acts as the reducing agent whereas Y is an oxidizing agent.

Reduction occurs at cathode whereas oxidation takes place at anode. So ${\text{A}}{{\text{l}}^{3+}}$  is reduced to form Al at cathode and Mg is oxidized to ${\text{M}}{{\text{g}}^{2+}}$  at anode.

The balanced reduction half-cell reaction at cathode is,

${\text{A}}{{\text{l}}^{3+}}+3{e^-}\to{\text{Al}}$

The balanced oxidation half-cell reaction at anode is,

${\text{Mg}}\to{\text{M}}{{\text{g}}^{2+}}+2{e^-}$

Learn more:

1. Which occur during redox reaction? brainly.com/question/1616320

2. Oxidation and reduction reaction: brainly.com/question/2973661

Answer details:

Grade: High School

Subject: Chemistry

Chapter: Redox reactions

Keywords: redox reaction, Mg, Mg2+, Al, Al3+, 2e-, 3e-, cathode, anode, half-cell reaction, oxidation, reduction, reductant, oxidant, reducing agent, oxidizing agent, electrons, redox pair, redox couple, oxidation state, oxidized, reduced, simultaneously, increase, decrease.