First, let's find the moles of hydrogen used to produce the ammonia
mol = mass ÷ molar mass
if the mass of hydrogen = 6.89 × 10⁻⁴ g
& the molar mass of hydrogen = 2 g/mol
then moles of hydrogen = (6.89 × 10⁻⁴ g) ÷ 2 g/mol
moles of H₂ = 3.445 × 10⁻⁴ mol
Next, balanced eq'n for the production of ammonia from hydrogen gas and nitrogen gas:
N₂ + 3H₂ → 2NH₃
Now, the mole ratio (ratio of the coefficients used to balance the equation) of H₂ : NH₃ is 3 : 2
∴ if the moles of H₂ = 3.445 × 10⁻⁴
then based on the mole ratio, the moles of NH₃ = [(3.445 × 10⁻⁴) ÷ 3] × 2
= (1.14833 × 10⁻⁴) × 2
∴ mole of NH₃ = 2.2967 × 10⁻⁴
Now, # of molecules = moles × Avogadro's Constant
∴ # of molecules of NH₃ = (2.2967 × 10⁻⁴) × (6.02 × 10²³)
= 1.383 × 10²⁰ molecules
Thus, the molecules of NH₃ produced is ≈ 1.38 × 10²⁰ molecules.
