Answer is: mass of ammonia is 17 grams.
Chemical reaction: 3H₂ + N₂ → 2NH₃.
m(N₂) = 14,01 g.
n(N₂) = m(N₂) ÷ M(N₂).
n(N₂) = 14,01 g ÷ 28,02.
n(N₂) = 0,5 mol.
m(H₂) = 3,02 g.
n(H₂) = 3,02 g ÷ 2,01 g/mol.
n(H₂) = 1,5 mol.
From chemical reaction: n(N₂) : n(H₂) = 1 : 3.
From chemical reaction: n(N₂) : n(NH₃) = 1 : 2.
n(NH₃) = 2 · 0,5 mol = 1 mol.
m(NH₃) = 1 mol · 17 g/mol.
m(NH₃) = 17 g.