Question

Given that ΔHo for the thermochemical equation

2 SO₂(g) + O₂(g) → 2SO₃(g)

is – 198 kJ, what is the enthalpy change for the decomposition of 1 mole of SO3 to give O₂ and SO₂, all in the gas state?

Answer 1

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.