[tex]\\ \tt\hookrightarrow 4NH_3+3O_2\longrightarrow 2NO+6H_2O[/tex]
#1
We can solve through ammonia or oxygen .Lets go through ammonia
Moles of Ammonia
[tex]\\ \tt\hookrightarrow \dfrac{12}{17}=0.7mol[/tex]
Moles of NO
[tex]\\ \tt\hookrightarrow 0.7(0.5)=0.35mol[/tex]
Mass of NO
#2
NH_3 is excess reagent and O_2 is limiting reagent .
#3
We need ∆n