How many moles of H2 are needed to produce 34.8 moles of NH3?

Moles H₂ needed = 52.2

A reaction coefficient is a number in the chemical formula of a substance involved in the reaction equation. The reaction coefficient is useful for equalizing reagents and products.

Reaction

N₂(g)+3H₂(g)⇒2NH₃(g)

From the reaction equation above, the reaction coefficient shows the mole ratio of reagents and products

moles NH₃ produced = 34.8

mol H₂: moles NH₃ = 3: 2, so moles H₂ :  

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.

in the analysis of systems that involve fluid flow, we frequently encounter the combination of properties u and pv.