Hydrogen gas reduces which metal ion in its aqueous solution?

Options

A. `Mg^(2+)`
B. `Li^(+)`
C. `Pd^(2+)`
D. `Zn^(3+)`

Answer

To determine which metal ion hydrogen gas can reduce in its aqueous solution, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Concept of Reduction**:
Reduction is a chemical reaction that involves the gain of electrons by a substance. In the context of metal ions, it refers to the conversion of a metal ion (in its oxidized state) to its elemental form.

2. **Review the Electrochemical Series**:
The electrochemical series, or reactivity series, ranks metals based on their reactivity. More reactive metals can displace less reactive metals from their compounds. Hydrogen is included in this series and is used as a reference point.

3. **Identify the Metals in the Options**:
The options provided are:
- Magnesium (Mg)
- Lithium (Li)
- Zinc (Zn)
- Palladium (Pd)

4. **Analyze Each Metal**:
- **Magnesium (Mg)**: Highly reactive, above hydrogen in the series. Cannot be reduced by hydrogen.
- **Lithium (Li)**: Also highly reactive, above hydrogen. Cannot be reduced by hydrogen.
- **Zinc (Zn)**: Less reactive than magnesium and lithium but still above hydrogen. Cannot be reduced by hydrogen.
- **Palladium (Pd)**: Less reactive than hydrogen and can be reduced by hydrogen.

5. **Conclusion**:
Since hydrogen can only reduce metal ions that are below it in the reactivity series, the only metal ion that can be reduced by hydrogen gas from the given options is **Palladium (Pd)**.

### Final Answer:
Hydrogen gas reduces **Palladium (Pd)** ion in its aqueous solution.

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