`K_(a)` for formic acid and acetic acid are `2.1xx10^(-4)` and `1.1xx10^(-5)` respectively. The relative strength of acids is:

Options

A. `19 : 1`
B. `2.3 : 1`
C. `1 : 2.1`
D. `4.37 : 1`

Explanation

To determine the relative strength of formic acid and acetic acid based on their acid dissociation constants (Ka), we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Acid Dissociation Constants**:
- Given:
- \( K_a \) for formic acid (HCOOH) = \( 2.1 \times 10^{-4} \)
- \( K_a \) for acetic acid (CH₃COOH) = \( 1.1 \times 10^{-5} \)

2. **Set Up the Ratio of the Acid Dissociation Constants**:
- The relative strength of the acids can be compared using the ratio of their \( K_a \) values:
\[ \text{Relative Strength} = \frac{K_{a \text{ (formic)}}}{K_{a \text{ (acetic)}}} \]

3. **Calculate the Ratio**:
- Substitute the values into the formula:
\[ \text{Relative Strength} = \frac{2.1 \times 10^{-4}}{1.1 \times 10^{-5}} \]

4. **Perform the Division**:
- First, divide the coefficients:
\[ \frac{2.1}{1.1} \approx 1.909 \quad (\text{approximately } 1.91) \]
- Next, divide the powers of ten:
\[ 10^{-4} \div 10^{-5} = 10^{(-4) - (-5)} = 10^{1} = 10 \]
- Therefore, the complete calculation is:
\[ \text{Relative Strength} \approx 1.91 \times 10 \approx 19.1 \]

5. **Take the Square Root**:
- Since we need the square root of the ratio to determine the relative strength:
\[ \sqrt{19.1} \approx 4.37 \]

6. **Conclusion**:
- The relative strength of formic acid to acetic acid is approximately \( 4.37 \). This indicates that formic acid is stronger than acetic acid.