Which of the following metals on treatement with alkali will liberate `H_(2)` gas?

Options

A. `Be`
B. `Sn`
C. `Ga`
D. `In`

Explanation

To determine which of the following metals will liberate hydrogen gas (H₂) when treated with alkali, we need to analyze the behavior of each metal in the presence of an alkali. The metals given are Beryllium, Tin, Gallium, and Indium.

### Step-by-Step Solution:

1. **Understand the Nature of the Metals**:
- Beryllium (Be), Tin (Sn), Gallium (Ga), and Indium (In) are all metals, but they have different chemical properties.
- Beryllium, Tin, and Gallium are known to be amphoteric metals, meaning they can react with both acids and bases.

2. **Reactions with Alkali**:
- Amphoteric metals can react with alkalis to form hydroxides and liberate hydrogen gas.
- The general reaction for an amphoteric metal (M) with an alkali (NaOH, for example) can be represented as:
\[ M + 2NaOH + 2H_2O \rightarrow M(OH)_2 + H_2 \uparrow \]
- This indicates that hydrogen gas (H₂) is produced during the reaction.

3. **Evaluate Each Metal**:
- **Beryllium (Be)**: Reacts with alkali to form beryllium hydroxide and liberates H₂.
- **Tin (Sn)**: Also reacts with alkali to form tin hydroxide and liberates H₂.
- **Gallium (Ga)**: Reacts similarly with alkali to form gallium hydroxide and liberates H₂.
- **Indium (In)**: Does not react with water or alkali to form hydroxide and does not liberate H₂.

4. **Conclusion**:
- The metals that will liberate hydrogen gas when treated with alkali are Beryllium, Tin, and Gallium.
- Indium does not liberate hydrogen gas under these conditions.

### Final Answer:
Beryllium, Tin, and Gallium will liberate H₂ gas when treated with alkali. Indium will not.