Which is the strongest acid (`pK_(a)` value is given)?

Options

A. `HCOOH[3.77]`
B. `C_(6)H_(5)COOH[4.22]`
C. `CH_(3)COOH[4.7]`
D. `CH_(3)CH_(2)COOH[4.88]`

Answer

To determine which is the strongest acid based on the provided pKa values, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Relationship Between pKa and Acidity**:
- Acidity is often measured using the dissociation constant (Ka) of an acid. The stronger the acid, the more it dissociates in solution, resulting in a higher concentration of hydrogen ions (H⁺).
- The relationship between pKa and Ka is given by the formula:
\[ \text{pKa} = -\log(\text{Ka}) \]
- A lower pKa value indicates a higher Ka value, which means a stronger acid.

2. **List the Given pKa Values**:
- For the acids provided, we have the following pKa values:
- Formic acid (HCOOH): 3.77
- Benzoic acid: 4.22
- Acetic acid: 4.7
- Propanoic acid: 4.8

3. **Compare the pKa Values**:
- To find the strongest acid, we need to identify which acid has the lowest pKa value.
- The pKa values are:
- HCOOH: 3.77
- Benzoic acid: 4.22
- Acetic acid: 4.7
- Propanoic acid: 4.8

4. **Identify the Strongest Acid**:
- Among the listed acids, formic acid (HCOOH) has the lowest pKa value of 3.77.
- Therefore, formic acid is the strongest acid among the options given.

5. **Conclusion**:
- The strongest acid based on the provided pKa values is **HCOOH (formic acid)**.