2NO + O₂ → 2NO₂
If mass of NO₂ = 1.31 g
then moles of NO₂ = [tex] \frac{MASS}{Molar Mass} [/tex] = [tex] \frac{1.31 g}{((14 * 1) + (16 * 2)) g / mol} [/tex]
= 0.0285 mol
The mole ratio of O₂ : NO₂ based on the equation is 1 : 2.
∴ if moles of NO₂ = 0.0285 mol
then moles of O₂ = 0.0285 mol ÷ 2
= 0.01425 mol
Grams of O₂ needed = mole × molar mass
= 0.01425 mol × (16 × 2) g/mol
= 0.456 g
