Equimoler solulition of HF, HCOOH and HCN at 298 K have the values of Ka as `6.8xx10^(-4), 1.8xx10^(-4)` and `4.8xx10^(-9)` respectively, what will be the order of their acidic strength ? (A)H F > H C N > H C O O H (B)H F > H C O O H > H C N (C)H C N > H F > H C O O H (D)H C O O H > H C N > H F

Options

A. `HFgtHCNgtHCOOH`
B. `HFgtHCOOHgtHCN`
C. `HCNgtHFgtHCOOH`
D. `HCOOHgtHCNgtHF`

Explanation

To determine the order of acidic strength for the given acids (HF, HCOOH, and HCN) based on their dissociation constants (Ka), we will follow these steps:

### Step 1: Understand the relationship between Ka and acidic strength
The strength of an acid is directly related to its dissociation constant (Ka). A higher Ka value indicates a stronger acid because it means that the acid dissociates more in solution, producing more hydrogen ions (H⁺).

### Step 2: List the given Ka values
- For HF (Hydrofluoric acid), Ka = 6.8 × 10^(-4)
- For HCOOH (Formic acid), Ka = 1.8 × 10^(-4)
- For HCN (Hydrogen cyanide), Ka = 4.8 × 10^(-9)

### Step 3: Compare the Ka values
Now, we will compare the Ka values to determine which acid is stronger:
- HF: 6.8 × 10^(-4) (highest)
- HCOOH: 1.8 × 10^(-4) (middle)
- HCN: 4.8 × 10^(-9) (lowest)

### Step 4: Determine the order of acidic strength
Based on the Ka values:
1. HF has the highest Ka, so it is the strongest acid.
2. HCOOH has a higher Ka than HCN, making it the second strongest.
3. HCN has the lowest Ka, making it the weakest acid.

Thus, the order of acidic strength from strongest to weakest is:
HF > HCOOH > HCN

### Conclusion
The correct answer is option (B): HF > HCOOH > HCN.

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