Which of the following metals does not give the following reaction? (M + water `rarr` oxide or hydroxide `+ H_(2 ))

Options

A. Iron
B. Sodium
C. Mercury
D. Magnesium

Answer

To determine which metal does not react with water to form an oxide or hydroxide while releasing hydrogen gas, we can analyze the reactivity of the given metals: iron, sodium, mercury, and magnesium.

### Step-by-Step Solution:

1. **Understand the Reaction**: The reaction we are considering is:
\[ \text{Metal (M)} + \text{Water (H}_2\text{O)} \rightarrow \text{Metal Oxide or Hydroxide} + \text{Hydrogen Gas (H}_2\text{)} \]
This reaction occurs when the metal is more reactive than hydrogen, meaning it can displace hydrogen from water.

2. **Review the Metals**: We have four metals to consider:
- **Sodium (Na)**
- **Magnesium (Mg)**
- **Iron (Fe)**
- **Mercury (Hg)**

3. **Check Reactivity**: Metals react with water based on their position in the electrochemical series:
- **Sodium**: Highly reactive, reacts vigorously with water.
- **Magnesium**: Reacts with water (especially steam) to form magnesium hydroxide and hydrogen.
- **Iron**: Reacts with water at elevated temperatures to form iron oxide and hydrogen.
- **Mercury**: Has a low reactivity and does not react with water to form an oxide or hydroxide.

4. **Determine Oxidation Potential**: The reactivity of metals can be assessed by their reduction potential:
- Sodium, magnesium, and iron have negative reduction potential values, indicating they are more reactive than hydrogen.
- Mercury has a positive reduction potential value, indicating it is less reactive than hydrogen.

5. **Conclusion**: Since mercury does not react with water to form an oxide or hydroxide and release hydrogen gas, it is the metal that does not give the specified reaction.

### Final Answer:
The metal that does not give the reaction \( M + \text{water} \rightarrow \text{oxide or hydroxide} + \text{H}_2 \) is **Mercury (Hg)**.

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