If S° for  ${\text{N}}_{\text{2}}{\text{,\hspace{0.17em}O}}_{\text{2}}{\text{,\hspace{0.17em}N}}_{\text{2}}{\text{O,\hspace{0.17em}NO,NO}}_{\text{2}}{\text{\hspace{0.17em}and\hspace{0.17em}N}}_{\text{2}}{\text{O}}_{\text{4}}\text{\hspace{0.17em}are}$ are 45.7, 49.0, 48.2, 50.24, 57.24 and 72.77 cal

respectively and ${\text{N}}_{\text{2}}\text{\hspace{0.17em}+\hspace{0.17em}}\frac{\text{1}}{\text{2}}{\text{\hspace{0.17em}O}}_{\text{2}}\rightleftharpoons {\text{\hspace{0.17em}N}}_{\text{2}}\text{O;\hspace{0.17em}ΔH°\hspace{0.17em}=\hspace{0.17em}19.49\hspace{0.17em}kcal\hspace{0.17em}at\hspace{0.17em}300\hspace{0.17em}K;\hspace{0.17em}}\frac{\text{1}}{\text{2}}{\text{N}}_{\text{2}}\text{\hspace{0.17em}+\hspace{0.17em}}\frac{\text{1}}{\text{2}}{\text{\hspace{0.17em}O}}_{\text{2}}\rightleftharpoons \text{\hspace{0.17em}NO;\hspace{0.17em}ΔH°\hspace{0.17em}=\hspace{0.17em}21.60\hspace{0.17em}kcal\hspace{0.17em}at\hspace{0.17em}300K}$

$\frac{\text{1}}{\text{2}}{\text{\hspace{0.17em}N}}_{\text{2}}{\text{\hspace{0.17em}+\hspace{0.17em}O}}_{\text{2}}\rightleftharpoons {\text{\hspace{0.17em}NO}}_{\text{2}}{\text{;\hspace{0.17em}ΔH°\hspace{0.17em}=\hspace{0.17em}8.09\hspace{0.17em}kcal\hspace{0.17em}at\hspace{0.17em}300\hspace{0.17em}K;\hspace{0.17em}N}}_{\text{2}}{\text{\hspace{0.17em}+\hspace{0.17em}2O}}_{\text{2}}\rightleftharpoons {\text{\hspace{0.17em}N}}_{\text{2}}{\text{O}}_{\text{4}}\text{;\hspace{0.17em}ΔH°\hspace{0.17em}=\hspace{0.17em}2.19\hspace{0.17em}kcal\hspace{0.17em}at\hspace{0.17em}300K}$ 

For which is more +ve: