J.R. S. answered 04/18/19
Ph.D. University Professor with 10+ years Tutoring Experience
Presumably you are referring to the reaction of nitrogen gas (N2) with hydrogen gas (H2) to produce ammonia gas (NH3).
N2(g) + 3H2(g) ==> 2NH3(g) ... balanced equation
1.5 moles H2 x 2 moles NH3/3 moles H2 x 17 g NH3/mole NH3 = 17 grams ammonia produced