Which cannot be used to generate `H_(2)`?

Options

A. `Al + NaOH`
B. `Zn + NaOH`
C. `Mg+NaOH`
D. `LiH + H_(2)O`

Explanation

To determine which of the given options cannot be used to generate hydrogen gas (H₂), we will analyze each option step by step.

### Step 1: Analyze Aluminium with NaOH
- Reaction: \( \text{Al} + \text{NaOH} + \text{H}_2\text{O} \rightarrow \text{NaAlO}_2 + \text{H}_2 \)
- This reaction produces sodium aluminate and hydrogen gas.
- **Conclusion**: Aluminium can generate H₂.

### Step 2: Analyze Zinc with NaOH
- Reaction: \( \text{Zn} + \text{NaOH} + \text{H}_2\text{O} \rightarrow \text{Na}_2\text{ZnO}_2 + \text{H}_2 \)
- This reaction also produces sodium zincate and hydrogen gas.
- **Conclusion**: Zinc can generate H₂.

### Step 3: Analyze Magnesium with NaOH
- Reaction: \( \text{Mg} + \text{NaOH} + \text{H}_2\text{O} \rightarrow \text{Mg(OH)}_2 + \text{Na} \)
- In this case, magnesium reacts with sodium hydroxide and water, but does not produce hydrogen gas.
- **Conclusion**: Magnesium does not generate H₂.

### Step 4: Analyze Lithium Hydride with Water
- Reaction: \( \text{LiH} + \text{H}_2\text{O} \rightarrow \text{LiOH} + \text{H}_2 \)
- This reaction produces lithium hydroxide and hydrogen gas.
- **Conclusion**: Lithium hydride can generate H₂.

### Final Conclusion
After analyzing all the options, we find that the reaction involving magnesium with sodium hydroxide does not produce hydrogen gas. Therefore, the correct answer is:

**Option C: Magnesium with NaOH cannot be used to generate H₂.**

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