Which of the following is the weakest base:-

Options

A. `NaOH`
B. `Zn(OH)_(2)`
C. `Ca(OH)_(2)`
D. `KOH`

Answer

To determine which of the given compounds is the weakest base among NaOH, Zn(OH)₂, Ca(OH)₂, and KOH, we can follow these steps:

### Step 1: Understand the Concept of Basicity
Basicity refers to the ability of a substance to accept protons or donate hydroxide ions (OH⁻) in solution. A stronger base will dissociate more readily to produce OH⁻ ions.

### Step 2: Identify the Types of Hydroxides
The compounds given are:
- NaOH (Sodium Hydroxide)
- Zn(OH)₂ (Zinc Hydroxide)
- Ca(OH)₂ (Calcium Hydroxide)
- KOH (Potassium Hydroxide)

### Step 3: Classify the Hydroxides
- NaOH and KOH are alkali metal hydroxides (Group 1).
- Ca(OH)₂ is an alkaline earth metal hydroxide (Group 2).
- Zn(OH)₂ is a hydroxide of a transition metal (d-block).

### Step 4: Compare Basic Strengths
1. **Alkali Metal Hydroxides (NaOH and KOH)**: These are strong bases because they dissociate completely in water to produce OH⁻ ions.
2. **Alkaline Earth Metal Hydroxides (Ca(OH)₂)**: These are generally weaker bases than alkali metal hydroxides but stronger than transition metal hydroxides.
3. **Transition Metal Hydroxides (Zn(OH)₂)**: These are typically the weakest bases among the hydroxides listed because they do not dissociate as readily to produce OH⁻ ions.

### Step 5: Conclusion
Based on the classification and comparison:
- NaOH and KOH are strong bases.
- Ca(OH)₂ is a weaker base than NaOH and KOH but stronger than Zn(OH)₂.
- Zn(OH)₂ is the weakest base among the options provided.

Thus, the weakest base among the given options is **Zn(OH)₂ (Zinc Hydroxide)**.

### Final Answer
**Zinc Hydroxide (Zn(OH)₂) is the weakest base.**

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