Enthalpy of Formation

Question

A scientist measures the standard enthalpy change for the following reaction to be -237.2 kJ :

2SO₂(g) + O₂(g)2SO₃(g)

Based on this value and the standard enthalpies of formation for the other substances, the standard enthalpy of formation of SO₃(g) is

in kj/mol

Answer 1

2SO₂(g) + O₂(g) ==> 2SO₃(g) ... ∆H = -237.2 kJ

Look up ∆Hºf for SO₂(g). The ∆Hºf for O₂(g) is zero.

Products - reactants = Reaction

2 x ∆Hºf SO₃(g) - 2 x ∆Hºf SO₂(g) = -237.2

∆Hºf SO3(g) = -237.2 / 2 x ∆Hºf SO₂(g) / 2 = answer