Occurs when Al(s) and CuCl2(aq) are mixed — Electrochemistry Chemistry Question

STEPS:

1. Identify the Reactants and Their States: The reaction involves solid aluminum metal ($Al$) and an aqueous solution of copper(II) chloride ($CuCl_2$). In solution, $CuCl_2$ exists as $Cu^{2+}$ and $Cl^-$ ions.
2. Determine the Initial Oxidation States: As an element in its standard state, $Al(s)$ has an oxidation number of 0. In the compound $CuCl_2$, copper has an oxidation number of +2.
3. Analyze the Activity Series/Reduction Potentials: According to the table of standard reduction potentials, the potential for $Cu^{2+} + 2e^- \rightarrow Cu(s)$ is $+0.34\text{ V}$, while for $Al^{3+} + 3e^- \rightarrow Al(s)$ it is $-1.66\text{ V}$. Because aluminum has a much more negative reduction potential, it is more easily oxidized than copper.
4. Describe the Electron Transfer: Aluminum atoms will spontaneously lose electrons (oxidation) to become $Al^{3+}$ ions, while copper ions in the solution will gain those electrons (reduction) to become solid copper metal.
5. Classify the Reaction: A chemical process characterized by the transfer of electrons between species, resulting in changes in oxidation numbers, is defined as an oxidation-reduction (redox) reaction.
6. Conclusion: The reaction is best represented by the net ionic equation $2 Al(s) + 3 Cu^{2+}(aq) \rightarrow 2 Al^{3+}(aq) + 3 Cu(s)$, confirming it is a redox process.

WHY_OTHERS_WRONG:

• Brønsted^-Lowry acid-base reaction (B): This type of reaction requires the transfer of a proton ($H^+$) from an acid to a base. There is no proton transfer occurring between these metallic species.
• Sublimation (C): Sublimation is a physical phase change where a solid turns directly into a gas (e.g., $I_2(s) \rightarrow I_2(g)$) and does not describe a reaction between two different substances in solution.
• Dehydration (D): Dehydration involves the removal of water from a chemical compound (such as driving water out of a hydrate), which is not relevant to the displacement of metal ions.
• Precipitation (E): A precipitation reaction occurs when two aqueous solutions are mixed to form an insoluble ionic solid (salt). While a solid (copper metal) is produced in this reaction, the underlying mechanism is electron transfer (redox) rather than the combination of ions to form an insoluble salt.