The formula for potassium nitrate is: 2KNO₃ → 2KNO₂ + O₂
If moles = mass ÷ molar mass
then moles of KNO₃ = 58.6 g ÷ [( 39 × 1 ) + ( 14 × 1) + ( 16 × 3)] g/mol
= 58.6 g ÷ ( 101 g ) g/mol
= 0.5802 mol
Now the mole ratio of KNO₃ : O₂ is 2 : 1
∴ if moles of KNO₃ = 0.5802 mol
then moles of O₂ = 0.5802 mol ÷ 2
= 0.2901 mol
Now since mass = moles × molar mass
∴ the mass of oxygen produced = 0.2901 mol × ( 16 × 2) g/mol
= 9.283 g
∴ the grams of oxygen gas produced when 58.6 grams of potassium nitrate is decomposed is ~ 9.28 g
