Which of the following hydroxides is most basic ?

Options

A. `Be(OH)_(2)`
B. `Ba(OH)_(2)`
C. `Ca(OH)_(2)`
D. `Mg(OH)_(2)`

Answer

To determine which hydroxide is the most basic among the given options, we need to consider the trend in basicity of hydroxides in the alkaline earth metals group (Group 2 of the periodic table).

### Step-by-Step Solution:

1. **Identify the Hydroxides**:
First, we need to identify the hydroxides we are comparing. Common hydroxides of alkaline earth metals include:
- Beryllium Hydroxide (Be(OH)₂)
- Magnesium Hydroxide (Mg(OH)₂)
- Calcium Hydroxide (Ca(OH)₂)
- Barium Hydroxide (Ba(OH)₂)

2. **Understand the Trend in Basicity**:
The basicity of hydroxides in the alkaline earth metals group increases as we move down the group. This is due to the increasing size of the metal cations, which affects their ability to ionize and release hydroxide ions (OH⁻) in solution.

3. **Analyze the Hydroxides**:
- **Beryllium Hydroxide (Be(OH)₂)**: Least basic, as beryllium is the smallest cation and has a strong covalent character.
- **Magnesium Hydroxide (Mg(OH)₂)**: More basic than beryllium hydroxide but less than calcium and barium hydroxides.
- **Calcium Hydroxide (Ca(OH)₂)**: More basic than magnesium hydroxide.
- **Barium Hydroxide (Ba(OH)₂)**: Most basic among the alkaline earth metal hydroxides due to the largest cation size, which allows for easier ionization and release of OH⁻ ions.

4. **Conclusion**:
Based on the trend, the most basic hydroxide among the options provided is **Barium Hydroxide (Ba(OH)₂)**.

### Final Answer:
**Barium Hydroxide (Ba(OH)₂) is the most basic hydroxide.**