Using the equation

N2+3H2-->2NH3

how many grams of hydrogen must react if the reaction needs to produce 31.75 grams of NH3?

Question options:

5.6

11.2

none of these

22.4

(Answer) 5.6 g

Mass of ammonia produced = 31.75 g

Moles of ammonia produced = (Mass / molar mass of ammonia)

= (31.75 g / 17.031 g / mol) = 1.86 moles.

According to the balanced chemical equation, mole ratio of hydrogen and ammonia = 3: 2

Moles of hydrogen needed to produce 1.86 moles of ammonia

= (3/2 x 1.86) moles = 2.79 moles

Mass of hydrogen needed = (Moles x molar mass of hydrogen)

= (2.79 x 2) g = 5.58 g = 5.6 g

Therefore, 5.6 g of hydrogen must react to produce 31.75 g of ammonia.