Given the following data:
2C(s) + H2(g) --> C2H2(g)
delta H° = 227.0 kJ
C2H2(g) + 5/2O2(g) --> 2CO2(g) + H2O(l)
delta H° = -1300.0 kJ
CO2(g) --> C(s) + O2(g)
delta H° = 393.5 kJ
Calculate delta H° for the reaction
H2O(l) --> H2(g) + 1/2O2(g)
Please help, I'm stuck :( thank you