Given the data in the table below, ΔH°_rxn for the reaction 2SO₂ (g) + O₂ (g) → 2SO₃ (g) Is ________ kJ. A)-99 B)99 C)-198 D)198 E)The ΔH°_f of O₂ (g)is needed for the calculation.

Question

Quizplus · Accepted Answer

According to Hess's Law, the overall enthalpy change for a reaction is the sum of the enthalpy changes for the individual steps of the reaction.

In this case, we can break down the reaction into two steps:

1. 2SO2 (g) + O2 (g) → 2SO3 (g) 
ΔH° = -198 kJ

2. 2SO3 (g) → 2SO2 (g) + O2 (g) 
ΔH° = +198 kJ

When we add these two steps together, we get:

2SO2 (g) + O2 (g) → 2SO3 (g) 
ΔH° = -198 kJ

This matches the overall reaction given in the question, so the answer is choice C (-198 kJ). We do not need to know the ΔH°f of O2 (g) for this calculation.

Given the Data in the Table Below, ΔH°rxn for the Reaction

Given the Data in the Table Below, ΔH°_rxn for the Reaction