Calculate the enthalpy change for the reaction:

2S(s) + 3O2(g) --> 2SO3(g)

Use the following thermochemical equations:

Reaction
S(s) + O2(g) --> SO2(g) Delta H(in kJ) -296.8
2SO2(g) + O2(g) --> 2SO3(g) Delta H(in kJ) -197.0

2 answers

Multiply equation 1 by 2 (multiply delta H by 2 also), add to equation 2 as is. Add deltaHs for total.
2NH2+ H2=2NH3...delta H=?