The values of dissociation constant of some bases are given below. Which is the weakest base ?

Options

A. `1.8 xx 10^(-5)`
B. `4.8 xx 10^(-10)`
C. `7.2 xx 10^(-11)`
D. `7.07 xx 10^(-7)`

Answer

To determine which is the weakest base among the given options based on their dissociation constants (Kb), we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Concept of Kb**:
The dissociation constant (Kb) for a base indicates its strength. A higher Kb value means the base dissociates more in solution, producing more hydroxide ions (OH⁻), which makes it a stronger base. Conversely, a lower Kb value indicates that the base is weaker because it dissociates less.

2. **Identify the Kb Values**:
From the question, we need to compare the Kb values of the bases provided. Assume the Kb values given are:
- Base A: Kb = 1.8 × 10⁻⁵
- Base B: Kb = 3.2 × 10⁻⁶
- Base C: Kb = 7.2 × 10⁻¹¹
- Base D: Kb = 1.0 × 10⁻¹⁴

3. **Compare the Kb Values**:
We need to identify which Kb value is the lowest.
- 1.8 × 10⁻⁵ (Base A)
- 3.2 × 10⁻⁶ (Base B)
- 7.2 × 10⁻¹¹ (Base C)
- 1.0 × 10⁻¹⁴ (Base D)

4. **Identify the Weakest Base**:
Among the Kb values listed, 7.2 × 10⁻¹¹ is the lowest. Therefore, the base corresponding to this Kb value is the weakest base.

5. **Conclusion**:
The base with the Kb value of 7.2 × 10⁻¹¹ is the weakest base among the options provided.

### Final Answer:
The weakest base is the one with Kb = 7.2 × 10⁻¹¹.

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