I. 21N2+23H2⇌NH3 Reverse and double the equation I 2NH3⇌N2+3H2⇒K1′=K121 II. 2NO⇌N2+O2 Reverse the equation II N2+O2⇌2NO⇒K2′=K21 Multiply by equation III 3H2+23O2⇌3H2O⇒K3′=K33 Required equation is 2NH3+25O2⟶2NO+3H2OK=K121⋅K21×K32=K12K2K33