Question

Calculate the amount of carbon dioxide that could be produced when 
(i) 1 mole of carbon is burnt in air. 
(ii) 1 mole of carbon is burnt in 16 g of dioxygen. 
(iii) 2 moles of carbon are burnt in 16 g of dioxygen.

Answer 1

Chemical equation

C(s) + O₂(g) → CO₂(g)

• 1 mol C reacts with 1 mol O₂ to give 1 mol CO₂.
• Molar mass: C = 12 g·mol⁻¹, O₂ = 32 g·mol⁻¹, CO₂ = 44 g·mol⁻¹.

(i) 1 mole of carbon burnt in air

• In air, O₂ is in excess; C is completely burnt.
• 1 mol C → 1 mol CO₂ → 44 g CO₂.

(i) CO₂ produced = 1 mol = 44 g.

(ii) 1 mole of carbon burnt in 16 g of dioxygen

• Given O₂ mass = 16 g.
• Moles of O₂ = 16 g ÷ 32 g·mol⁻¹ = 0.5 mol.
• Only 0.5 mol C can react (O₂ is limiting), giving 0.5 mol CO₂.

CO₂ formed = 0.5 mol × 44 g·mol⁻¹ = 22 g

(ii) CO₂ produced = 0.5 mol = 22 g.

(iii) 2 moles of carbon burnt in 16 g of dioxygen

• Moles of C = 2 mol; moles of O₂ = 16 ÷ 32 = 0.5 mol.
• O₂ is still limiting; only 0.5 mol C can burn.
• So again, 0.5 mol CO₂ is produced.

CO₂ formed = 0.5 mol × 44 g·mol⁻¹ = 22 g

(iii) CO₂ produced = 0.5 mol = 22 g.