The formula for lithium chlorate is: 2LiClO₃ → 2LiCl + 3O₂
If moles = mass ÷ molar mass
then moles of LiClO₃ = 38.7 g ÷ [( 7 × 1 ) + ( 35.5 × 1) + ( 16 × 3)] g/mol
= 38.7 g ÷ ( 90.5 g ) g/mol
= 0.428 mol
Now the mole ratio of LiClO₃ : O₂ is 2 : 3
∴ if moles of LiClO₃ = 0.428 mol
then moles of O₂ = ( 0.428 mol ÷ 2 ) × 3
= 0.642 mol
Now since mass = moles × molar mass
∴ the mass of oxygen produced = 0.642 mol × ( 16 × 2) g/mol
= 20.544 g
∴ the grams of oxygen gas produced when 38.7 grams of lithium chlorate is decomposed is ~ 20.54 g.