Thermodynamics?

Question

I need to calculate the heat of reaction in kJ/mol for the reaction
SO2 + H2 + O2 produce H2SO4 given the following information
S + O2 = SO2 delta H = -297.1 kJ/mol
H2 +S +2O2 =H2SO4 delta H= -811.7 kJ/mol

Answer 1

SO2 + H2 + O2= H2SO4
ΔH(reaction)= ΔH(products)-ΔH(reactants)
or,ΔH(reaction)= ΔH(H2SO4)- ΔH(SO2)- ΔH(H2)- ΔH(O2)
H2 & O2 are in elemental state so ΔH(H2)=ΔH(O2)=0
ΔH(H2SO4) = -811.7 kJ/mol
ΔH(SO2)=-297.1 kJ/mol
Hence, ΔH(reaction)=-811.7+297.1 = -514.6 kJ/mol

Answer 2

Reverse 1st reaction and add it it to the 2nd.

So, heat of reaction = 297.1-811.7 = -514 kJ.mol