Enthalpy Change

Step 1: Understanding the Concept:
Hess's Law: Enthalpy change is independent of path.

Step 2: Detailed Explanation:
Given:
(1) C(s) + O (g) CO (g); kJ/mol
(2) CO(g) + 1/2 O (g) CO (g); kJ/mol
Subtract (2) from (1):
C(s) + 1/2 O (g) CO(g); kJ/mol.

Step 3: Final Answer:
kJ

Step 1: Understanding the Concept:
More negative enthalpy of formation indicates greater stability of the compound.

Step 2: Detailed Explanation:
The enthalpy of formation ( ) for HF is -161 kJ/mol, and for HCl is -92 kJ/mol. • A more negative means the compound is more stable (lower in energy). • Since -161 < -92, HF is more stable than HCl. • The greater stability of HF indicates a stronger H-F bond and a higher affinity of fluorine for hydrogen compared to chlorine. • Both values are negative, so both compounds are exothermic. Statement (B) is the opposite of the correct fact.

Step 3: Final Answer:
The incorrect statement is that HCl is more stable than HF, which corresponds to option (B).