A metal having negative reduction potential, when dipped in the solution of its own ions, has a tend — Electrochemistry Chemistry Question

💡 Solution & Explanation

Step 1 - Understand the Processes at the Metal-Solution Interface When a metal rod ($\ce{M}$) is immersed in an aqueous solution of its own metal ions ($\ce{M^{n+}}$), two opposing chemical processes compete at the boundary interface: 1. **Oxidation (Dissolution):** Metal atoms on the surface of the rod lose electrons and pass into the solution as positively charged metal cations: $$\ce{M(s) -> M^{n+}(aq) + n e^-}$$ This process leaves behind excess electrons on the metal rod, tending to make the electrode negatively charged relative to the solution. 2. **Reduction (Deposition):** Metal cations present in the solution collide with the electrode, gain electrons from it, and deposit as neutral metal atoms on the rod: $$\ce{M^{n+}(aq) + n e^- -> M(s)}$$ This process removes electrons from the metal rod, tending to make the electrode positively charged relative to the solution. Step 2 - Correlation with Negative Reduction Potential The thermodynamic tendency of these two competing processes is determined by the standard reduction potential ($E^\circ_{\text{red}}$) of the metal: * A **negative standard reduction potential** ($E^\circ_{\text{red}} < 0$) indicates that the metal has a very weak tendency to gain electrons and undergo reduction compared to the standard hydrogen electrode (SHE). * Consequently, such a metal possesses a positive standard oxidation potential ($E^\circ_{\text{ox}} > 0$), meaning it has a strong spontaneous tendency to undergo oxidation (lose electrons). * Therefore, when a metal with a negative reduction potential is dipped in a solution of its own ions, the oxidation reaction ($\ce{M -> M^{n+} + n e^-}$) dominates. The metal atoms spontaneously lose electrons and dissolve into the solution as positive cations, meaning they have a tendency to **become electrically positive** species. Step 3 - Discussion of the Options * **Option (A) is incorrect:** Because the metal has a negative reduction potential, it is highly reactive and has a strong tendency to react rather than remaining inert as neutral metal atoms. * **Option (B) is correct:** The metal atoms lose electrons to form positively charged metal ions ($\ce{M^{n+}}$) and dissolve into the solution, thus demonstrating a tendency to "become electrically positive". * **Option (C) is incorrect:** While the accumulation of released electrons on the solid metal rod makes the electrode itself electrically negative with respect to the solution, the question refers to the chemical state of the metal species that reacts. The metal atoms themselves lose electrons and convert into positive ions (cations) in the solution. * **Option (D) is incorrect:** Deposition is a reduction process. Since the reduction potential is negative, the tendency for the metal ions to gain electrons and deposit as solid metal is extremely weak compared to the tendency for oxidation. $$\text{Correct Option: } \boxed{\text{B}}$$