Which of the following is a weak base?

Options

A. NaOH
B. KOH
C. `NH_4 OH`
D. None of these

Answer

To determine which of the following is a weak base, we need to understand the characteristics of weak and strong bases.

### Step-by-Step Solution:

1. **Understand the Definition of Weak and Strong Bases**:
- A **strong base** completely dissociates in water, producing a high concentration of hydroxide ions (OH⁻).
- A **weak base** only partially dissociates in water, resulting in a lower concentration of hydroxide ions.

2. **Identify Common Bases**:
- Common strong bases include sodium hydroxide (NaOH) and potassium hydroxide (KOH).
- A common weak base is ammonium hydroxide (NH₄OH).

3. **Analyze the Given Compounds**:
- If the question provides a list of compounds, we need to evaluate each one based on their dissociation in water.
- For example, if the options include NaOH, KOH, and NH₄OH, we can analyze them:
- NaOH and KOH are strong bases because they dissociate completely in water.
- NH₄OH is a weak base because it does not dissociate completely and results in a lower concentration of OH⁻ ions in solution.

4. **Conclusion**:
- Based on the analysis, the weak base among the given options is NH₄OH (ammonium hydroxide).

### Final Answer:
The weak base is **NH₄OH (ammonium hydroxide)**.