To determine which half-reaction correctly describes the oxidation process for the given redox reaction:
[tex]\[ Zn (s) + 2 HCl (aq) \longrightarrow ZnCl_2 (aq) + H_2 (g) \][/tex]
First, we need to identify the species that are being oxidized and reduced.
Step-by-Step Solution:
1. Identify Oxidation and Reduction:
- In a redox reaction, oxidation is the process of losing electrons, while reduction is the process of gaining electrons.
- Here, zinc (\(Zn (s)\)) and hydrogen ions (\(H^+ (aq)\)) from hydrochloric acid (\(HCl (aq)\)) are involved.
2. Zn Oxidation:
- Zinc (\(Zn\)) starts in a solid metallic form and ends as zinc ions (\(Zn^{2+}\)) in solution.
- The transition from \(Zn (s)\) to \(Zn^{2+} (aq)\) involves the loss of electrons:
[tex]\[ Zn (s) \longrightarrow Zn^{2+} (aq) + 2e^{-} \][/tex]
- This half-reaction shows zinc (\(Zn\)) losing two electrons to form \(Zn^{2+}\), indicating oxidation.
3. Analyze the Options:
Let's review each provided half-reaction option to determine which correctly describes oxidation:
- Option 1: \(Zn^{2+} (s) + 2e^{-} (aq) \longrightarrow Zn (s)\)
- This represents zinc ions (\(Zn^{2+}\)) gaining electrons to form solid zinc (\(Zn\)), which is a reduction process, not oxidation.
- Option 2: \(Zn (s) \longrightarrow Zn^{2+} (aq) + 2e^{-}\)
- This shows solid zinc (\(Zn\)) losing electrons to form zinc ions (\(Zn^{2+}\)), correctly describing the oxidation process.
- Option 3: \(2 H^+ + 2e^{-} \longrightarrow H_2\)
- This represents hydrogen ions (\(H^+\)) gaining electrons to form hydrogen gas (\(H_2\)), which is a reduction process, not oxidation.
- Option 4: \(H_2 + 2e^{-} \longrightarrow 2 H^+\)
- This shows hydrogen gas (\(H_2\)) losing electrons to form hydrogen ions (\(H^+\)), which describes an oxidation process for hydrogen but not for zinc.
4. Conclusion:
- Based on the analysis, the correct half-reaction that describes the oxidation process for zinc (\(Zn\)) in the given redox reaction is:
[tex]\[
Zn (s) \longrightarrow Zn^{2+} (aq) + 2e^{-}
\][/tex]
Thus, the correct option is Option 2.
