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Given the equation representing a reaction:
[tex]$
Cd + NiO_2 + 2 H_2O \rightarrow Cd(OH)_2 + Ni(OH)_2
$[/tex]

Which half-reaction equation represents the oxidation in the reaction?

A. [tex]\( Ni^{4+} + 2 e^{-} \rightarrow Ni^{2+} \)[/tex]
B. [tex]\( Ni^{4+} \rightarrow Ni^{2+} + 2 e^{-} \)[/tex]
C. [tex]\( Cd \rightarrow Cd^{2+} + 2 e^{-} \)[/tex]
D. [tex]\( Cd + 2 e^{-} \rightarrow Cd^{2+} \)[/tex]



Answer :

GinnyAnswer
To determine which half-reaction represents the oxidation part of the given reaction, we need to identify which species loses electrons during the reaction. Oxidation refers to the loss of electrons, while reduction refers to the gain of electrons.

Given the equation for the overall reaction:
[tex]$ Cd + NiO_2 + 2 H_2O \rightarrow Cd(OH)_2 + Ni(OH)_2 $[/tex]

Let's examine the species involved:

1. Cadmium (Cd):
- On the reactant side, cadmium is in its elemental form, Cd.
- On the product side, cadmium is part of cadmium hydroxide, Cd(OH)_2.

Cadmium goes from Cd (0) to Cd(OH)_2, where its oxidation state is +2 (Cd^2+).

2. Nickel (Ni) in NiO_2:
- In NiO_2, nickel is in the +4 oxidation state (Ni^4+).
- On the product side, nickel is part of nickel hydroxide, Ni(OH)_2, where its oxidation state is +2 (Ni^2+).

To identify the oxidation half-reaction, we need to look for the species that loses electrons (oxidation). Cadmium (Cd) goes from 0 to +2, indicating a loss of two electrons:
[tex]$ Cd \rightarrow Cd^{2+} + 2e^- $[/tex]

This represents the oxidation half-reaction.

Therefore, the correct answer is:
(3) [tex]\( Cd \rightarrow Cd^{2+} + 2 e^{-} \)[/tex]

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