confused on Hess's law...?
Calculate the heat of reaction in kJ/mol for the reaction: H2 + SO2 + O2 --> H2SO4
GIVEN: S + O2 --> SO2 , energy = -297.1 kJ/mol
H2 + S + 2O2 --> H2SO4 , energy = -811.7 kJ/mol
Calculate the heat of reaction in kJ/mol for the reaction: H2 + SO2 + O2 --> H2SO4
GIVEN: S + O2 --> SO2 , energy = -297.1 kJ/mol
H2 + S + 2O2 --> H2SO4 , energy = -811.7 kJ/mol
Comments
H₂ + SO₂ + O₂ → H₂SO₄
Reverse the first reaction given (and the sign of ∆H) and add it to the second:
H₂ + S + 2O₂ → H₂SO₄ , . . . . ∆H = –811.7 kJ/mol
. . . . . . . SO₂ → S + O₂ , . . . . ∆H = +297.1 kJ/mol
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H₂ + SO₂ + O₂ → H₂SO₄ . . . . ∆H = –514.6 kJ/mol
Species on both sides cancel each other out.