N2(g)+3H2O(l)=2NH3(g)+1.5O2(g),△H.
已知:N2(g)+3H2(g)=2NH3(g)△H=a kJ/mol,
2H2(g)+O2(g)=2H2O(l)△H=b kJ/mol,
则N2(g)+3H2O(l)=2NH3(g)+1.5O2(g)的△H=kJ/mol(用含a、b的式子表示).