Which of the following anions is the weakest base ?

Options

A. `C_2H_5O^(-)`
B. `NO_3^(-)`
C. `F^(-)`
D. `CH_3COO^(-)`

Answer

To determine which of the following anions is the weakest base, we can follow these steps:

### Step 1: Understand the relationship between acids and bases
- Recall that the strength of a base is inversely related to the strength of its conjugate acid. This means that the stronger the acid, the weaker its conjugate base will be.

### Step 2: Identify the acids associated with the given anions
- We need to identify the conjugate acids for the anions provided in the options. For example:
- If one of the anions is NO3⁻, its conjugate acid is HNO3 (nitric acid).
- If another anion is ClO4⁻, its conjugate acid is HClO4 (perchloric acid).
- Similarly, for other anions, identify their conjugate acids.

### Step 3: Determine the strength of the acids
- Compare the strengths of the identified acids:
- HNO3 is a strong acid.
- HClO4 is also a strong acid.
- Other acids like H2CO3 (carbonic acid) are weaker.

### Step 4: Conclude which anion is the weakest base
- Since the strength of the conjugate base decreases as the strength of the acid increases, the anion that corresponds to the strongest acid will be the weakest base.
- In this case, since HNO3 is one of the strongest acids, its conjugate base NO3⁻ will be the weakest base among the options.

### Final Answer
- Therefore, the weakest base among the given anions is NO3⁻.