the balanced chemical equation for the formation of NH₃ is given below
N₂ + 3H₂ --> 2NH₃
stoichiometry of H₂ to NH₃ is 3 : 2
Mass of H₂ reacted - 7.26 x 10⁻⁴ g
number of H₂ moles - 7.26 x 10⁻⁴ g / 2 g/mol = 3.63 x 10⁻⁴ mol
when 3 mol of H₂ reacts - 2 mol of NH₃ is formed
Therefore when 3.63 x 10⁻⁴ mol of H₂ reacts - 2/3 x 3.63 x 10⁻⁴ mol of NH₃
Number of NH₃ moles formed - 2.42 x 10⁻⁴ mol
Since 1 mol of NH₃ is made of 6.022 x 10²³ molecules
NH₃ molecules formed - 6.022 x 10²³ molecules /mol x 2.42 x 10⁻⁴ mol
= 1.46 x 10²⁰ molecules of NH₃ formed