Answer:
7.5 moles of hydrogen would be needed to consume available nitrogen.
Explanation:
First of all we will write the balance chemical equation.
3H₂ + N₂ → 2NH₃
Number of moles of hydrogen:
number of moles = mass / molar mass
number of moles = 7 g/ 2 g/mol
number of moles = 3.5 mol
Number of moles of nitrogen:
number of moles = mass / molar mass
number of moles = 70 g/ 28 g/mol
number of moles = 2.5 mol
Now we compare the moles of hydrogen and nitrogen with ammonia from balance chemical equation.
N₂ : NH₃
1 : 2
2.5 : 2×2.5 = 5 mol
H₂ : NH₃
3 : 2
3.5 ; 2/3×3.5 =2.3 mol
So the number of moles of ammonia produced from hydrogen are less, hydrogen will be limitting reactant.
The amount of ammonia left:
H₂ : N₂
3 : 1
3.5 : 1/3×3.5 = 1.2 mol
So the 1.2 moles of nitrogen are react completely with 3.5 moles of hydrogen.
moles of ammonia left = 2.5 - 1.2 = 1.3 moles
If 7.5 moles of hydrogen present:
H₂ : N₂
3 : 1
7.5 : 1/3×7.5 = 2.5 mol
It means 7.5 mole of hydrogen will consume 2.5 moles of ammonia.