Which metal can not obtained by electrolysis of their aqueous salt solution ?

Options

A. Silver
B. Magnesium
C. Copper
D. Platinum

Answer

To determine which metal cannot be obtained by electrolysis of their aqueous salt solution, we will analyze each option based on the discharge potentials of the metal ions compared to the hydrogen ions.

### Step-by-Step Solution:

1. **Understanding Electrolysis**:
- Electrolysis involves passing an electric current through an electrolyte to cause a chemical change. In the case of aqueous solutions, we need to consider the ions present and their discharge potentials.

2. **Analyzing Silver (Ag)**:
- The aqueous solution of silver consists of Ag⁺ ions, H⁺ ions, and OH⁻ ions.
- The discharge potential of Ag⁺ is lower than that of H⁺. Therefore, during electrolysis, Ag⁺ ions will be reduced at the cathode, resulting in the deposition of silver.
- **Conclusion**: Silver can be obtained by electrolysis.

3. **Analyzing Magnesium (Mg)**:
- The aqueous solution of magnesium consists of Mg²⁺ ions, H⁺ ions, and OH⁻ ions.
- The discharge potential of Mg²⁺ is higher than that of H⁺. This means that H⁺ ions will be reduced at the cathode instead of Mg²⁺ ions.
- **Conclusion**: Magnesium cannot be obtained by electrolysis.

4. **Analyzing Copper (Cu)**:
- The aqueous solution of copper consists of Cu²⁺ ions, H⁺ ions, and OH⁻ ions.
- The discharge potential of Cu²⁺ is lower than that of H⁺. Thus, Cu²⁺ ions will be reduced at the cathode, leading to the deposition of copper.
- **Conclusion**: Copper can be obtained by electrolysis.

5. **Analyzing Platinum (Pt)**:
- The aqueous solution of platinum consists of Pt²⁺ and Pt³⁺ ions, H⁺ ions, and OH⁻ ions.
- The discharge potential of Pt²⁺ and Pt³⁺ is lower than that of H⁺. Therefore, platinum ions will be reduced at the cathode, resulting in the deposition of platinum.
- **Conclusion**: Platinum can be obtained by electrolysis.

6. **Final Conclusion**:
- After analyzing all options, the metal that cannot be obtained by electrolysis of their aqueous salt solution is **Magnesium**.

### Answer:
**Magnesium cannot be obtained by electrolysis of their aqueous salt solution.**

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