Question

spontaneous redox reaction happens between zinc (Zn) and magnesium (Mg) in an electrochemical cell. (6 points) i. Use the reduction potential chart to determine which metal is oxidized and which is reduced. (1 point) ii. Write the half-reactions for this reaction, indicating the oxidation half-reaction and the reduction half-reaction. (1 point) iii. Which metal is the anode, and which is the cathode

Answer 1

Answer:

For (i): Magnesium is getting oxidized and zinc is getting reduced.

For (ii): The half reactions are given below.

For (iii): Magnesium will act as anode and zinc act as cathode.

Explanation:

• For (i):

$E^o_{(Mg^{2+}/Mg)}=-2.37V\\E^o_{(Zn^{2+}/Zn)}=-0.76V$

The substance having highest positive $E^o$ potential will always get reduced and will undergo reduction reaction. Here, zinc will always undergo reduction reaction will get reduced.

Magnesium will undergo oxidation reaction and will get oxidized.

• For (ii):

Oxidation reaction is defined as the reaction in which an atom looses its electrons. The oxidation number of the atom gets increased during this reaction.

$X\rightarrow X^{n+}+ne^-$

Reduction reaction is defined as the reaction in which an atom gains electrons. The oxidation number of the atom gets reduced during this reaction.

$X^{n+}+ne^-\rightarrow X$

Oxidation half reaction:  $Mg\rightarrow Mg^{2+}+2e^-$

Reduction half reaction:  $Zn^{2+}+2e^-\rightarrow Zn$

• For (iii):

Oxidation reaction always occurs on anode side and thus, magnesium is acting as anode.

Reduction reaction always occurs on cathode side and thus, zinc is acting as cathode.