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

Monjur Alahi

Enthalpy of formation of `HF` and `HCl` are `-161 kJ` and `-92 kJ` respectively. Which of the following statements is incorrect ?
A. The affinity of fluorine to hydrogen is greater than the affinity of chlorine to hydrogen
B. `HF` is more stable than `HCl`
C. `HCl` is more stable than `HF`
D. `HF` and `HCl` are endothermic compounds.


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Correct Answer - C
Compound for which `DEltaH_(f)` is negative is more stable than the compound for which `DeltaH_(f)` is positive. In other words, exothermic compounds are more stable than endothermic compounds. Further, for exothermic compound, more the heat evolved during the formation of a compound from its elements, more stable it is. As such `HF` with `DeltaH_(f)=-161kJ` is more stable than `HCl` with `DeltaH_(f)=-92 kJ`.

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