6.Calculate H for the reaction 4 NH3 (g) + 5 O2 (g)  4 NO (g) + 6 H2O (g), from the following data.
N2 (g) + O2 (g)  2 NO (g) H = -180.5 kJ
N2 (g) + 3 H2 (g)  2 NH3 (g) H = -91.8 kJ
2 H2 (g) + O2 (g)  2 H2O (g) H = -483.6 kJ

7.Calculate H for the reaction CH4 (g) + NH3 (g)  HCN (g) + 3 H2 (g), given:
N2 (g) + 3 H2 (g)  2 NH3 (g) H = -91.8 kJ
C (s) + 2 H2 (g)  CH4 (g) H = -74.9 kJ
H2 (g) + 2 C (s) + N2 (g)  2 HCN (g) H = +270.3 kJ