Mass of N₂ will be formed : 50.12 g
Reaction
2 NH₃(g) + 3 CuO(s) → N₂(g) + 3 Cu(s) + 3 H₂O(g)
moles NH₃ = 3.58
ratio mol NH₃ : mol N₂ = 2 : 1
so mol N₂ :
[tex]\tt \dfrac{1}{2}\times 3.58=1.79[/tex]
mass N₂ (MW=28 g/mol) :
[tex]\tt 1.79\times 28=50.12~g[/tex]