Final answer:
The enthalpy change for the decomposition of 1 mole of SO3 to form SO2 and O2 is +99 kJ.
Step-by-step explanation:
Enthalpy Change Calculation
The student is interested in calculating the enthalpy change for the decomposition reaction based on the provided thermochemical equation. The given reaction is an exothermic process. According to the problem, 2 moles of SO3 decompose to give 2 moles of SO2 and 1 mole of O2, releasing -198 kJ of energy. To find the enthalpy change for the decomposition of 1 mole of SO3, we shall rewrite the reaction in reverse:
2SO3(g) → 2SO2(g) + O2(g) ΔH = +198 kJ
Since we seek the enthalpy for just 1 mole of SO3, we halve the equation and its associated enthalpy:
SO3(g) → SO2(g) + ½O2(g) ΔH = +99 kJ
Thus, the enthalpy change for the decomposition of 1 mole of SO3 (to form SO2 and O2) is +99 kJ.