已知:①N2(g)+O2(g)=2NO(g)△H=+180.5kJ/mol②N2(g)+3H2(g)?2NH3(g)△H=-92.4kJ/mol③2H2(g)+O2(g)=2H2O(g)△H=-483.6kJ/mol由盖斯定律可知,①×2-②×2+③×3得:4NH3(g)+5O2(g)═4NO(g)+6H2O(g)△H=-905.0kJ/mol故答案为:4NH3(g)+5O2(g)═4NO(g)+6H2O(g)△H=-905.0kJ/mol.