Problem: The ΔH for the oxidation of sulfur in the gas phase to SO3 is -204 kJ/mol and for the oxidation of SO2 to SO3 is 89.5 kJ/mol.Find the enthalpy of formation of SO2 under these conditions.

FREE Expert Solution

We are asked to find the enthalpy of formation of SO2 under these conditions.

The oxidization of sulfur to SO3 is the formation reaction for SO3. Therefore, the enthalpy of reaction is the enthalpy of formation for SO3.


Balanced reaction: 

2 SO2(g) + O2(g) → 2 SO3(g)


ΔH°rxn=ΔH°f, prod-ΔH°f, react


Note that we need to multiply each ΔH˚f by the stoichiometric coefficient since ΔH˚f is in kJ/mol. 

Also, note that ΔH˚f for elements in their standard state is 0.



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Problem Details

The ΔH for the oxidation of sulfur in the gas phase to SO3 is -204 kJ/mol and for the oxidation of SO2 to SO3 is 89.5 kJ/mol.

Find the enthalpy of formation of SO2 under these conditions.

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