Which equation represents a decomposition reaction?
(1) caco3(s) ==> cao(s) + co2(g)
(2) cu(s) + 2agno3(aq) ==> 2ag(s) + cu(no3)2(aq)
(3) 2h2(g) + o2(g) ==> 2h2o(l)
(4) koh(aq) + hcl(aq) ==> kcl(aq) + h2o(l)

n2(g) + 3h2-> 2nh3(g)   this is the balanced equation

note the mole ratio between n2, h2 and nh3.   it is 1 : 3 : 2   this will be important.

moles n2 present = 28.0 g n2 x 1 mole n2/28 g = 1 mole n2 present

moles h2 present = 25.0 g h2 x 1 mole h2/2 g = 12.5 moles h2 present

based on mole ratio, n2 is limiting in this situation because there is more than enough h2 but not enough n2.

moles nh3 that can be produced = 1 mole n2 x 2 moles nh3/mole n2 = 2 moles nh3 can be produced

grams of nh3 that can be produced = 2 moles nh3 x 17 g/mole = 34 grams of nh3 can be produced

note:   the key to this problem is recognizing that n2 is limiting, and therefore limits how much nh3 can be produced.

fun caring loving person