1 mole = 6.023 $\times$ 10²³ number of molecules.

1 g mole of O₂ = 32 g of O₂

$\Rightarrow$ 16 g of O₂ = 0.5 g mole of O₂

1 g mole of N₂ = 28 g of N₂

$\Rightarrow$ 7 g of N₂ = 0.25 g mole of N₂

1 g mole of H₂ = 2 g of H₂

$\Rightarrow$ 2 g of H₂ = 1 g mole of H₂

1 g of NO₂ = 14 + 16 $\times$ 2 = 46

$\Rightarrow$ 16 g of NO₂ = 0.35 mole NO₂