J.R. S. answered 02/01/19
Ph.D. University Professor with 10+ years Tutoring Experience
First, write a correctly balanced equation for the reaction taking place:
N2(g) + 3H2(g) ==> 2NH3(g)
From the stoichiometry of the balanced equation, 2 moles NH3 are formed from 3 moles H2.
Grams of hydrogen (H2) reacted = 1.7 moles NH3 x 3 moles H2/2 moles NH3 x 2 g H2/mole H2 = 5.1 g H2