Enthalpy of formation of `HF` and `HCl` are `-161 kJ` and `-92 kJ` respectively. Which of the following statements is incorrect ?

Options

A. HCl is more stable than HF
B. Formation of HF and HCl are exothermic reaction
C. The affinity of fluorine to hydrogen is greater than the affinity of chlorine to hydrogen
D. HF is more stable than HCl

Explanation

To determine which statement is incorrect regarding the enthalpy of formation of HF and HCl, we can analyze the given data and the properties of these compounds step by step.

### Step 1: Understand Enthalpy of Formation
The enthalpy of formation (ΔH_f) of a compound is defined as the heat change that occurs when one mole of the compound is formed from its elements in their standard states. The values given are:
- ΔH_f (HF) = -161 kJ
- ΔH_f (HCl) = -92 kJ

### Step 2: Analyze Stability Based on Enthalpy Values
The more negative the enthalpy of formation, the more stable the compound is. This is because a lower enthalpy indicates that more energy is released during the formation of the compound, suggesting that the compound is more stable.

- Since ΔH_f (HF) is -161 kJ, and ΔH_f (HCl) is -92 kJ, HF is more stable than HCl because it has a more negative enthalpy of formation.

### Step 3: Evaluate the Statements
Now, we need to evaluate the statements provided in the question based on our understanding:

1. **HCl is more stable than HF.** (This is incorrect based on our analysis.)
2. **The formation of HF and HCl are exothermic.** (This is correct since both ΔH_f values are negative.)
3. **The affinity of Fluorine to Hydrogen is greater than the affinity of Chlorine to Hydrogen.** (This is correct because Fluorine is more electronegative than Chlorine.)
4. **HF is more stable than HCl.** (This is correct based on the enthalpy values.)

### Conclusion
The incorrect statement is: **HCl is more stable than HF.**