Final answer:
The enthalpy change for the reaction O2 (g) + O(g) → O3(g) is -106.5 kJ/mol, calculated using the standard enthalpy of formation values for O3(g) and O(g), and recognizing that ∆Hf° for O2 is zero.
Step-by-step explanation:
To calculate the enthalpy change (∆H°) for the reaction O2 (g) + O(g) → O3(g), we use the standard enthalpy of formation values provided for O3(g) and O(g).
The standard enthalpy of formation (∆Hf°) is the heat change when one mole of a substance is formed from its elements in their standard states.
In this case, we are given ∆Hf° = 142.7 kJ/mol for O3(g) and ∆Hf° = 249.2 kJ/mol for O(g).
The enthalpy change of the reaction (∆H°) is calculated using the formula:
∆H° = ∆Hf° (products) - ∆Hf° (reactants)
For the reaction under consideration:
∆H° = ∆Hf° (O3) - [∆Hf° (O2) + ∆Hf° (O)]
Where ∆Hf° (O2) is zero for elemental oxygen in its standard state. Thus:
∆H° = 142.7 kJ/mol (for O3) - [0 kJ/mol (for O2) + 249.2 kJ/mol (for O)]
∆H° = 142.7 kJ/mol - 249.2 kJ/mol
= -106.5 kJ/mol
Therefore, the enthalpy change for the formation of ozone from oxygen and atomic oxygen is -106.5 kJ/mol.