What volume of carbon(II) oxide is produced by reacting excess carbon with 10 dm³ of oxygen?

Correct answer: 20 dm³

Explanation: For the formation of carbon(II) oxide (CO), the reaction is:
2C(s) + O₂(g) → 2CO(g)

From the balanced equation, 1 volume of O₂ produces 2 volumes of CO (at the same temperature and pressure). Therefore, with 10 dm³ of O₂:

Volume of CO = 2 × 10 dm³ = 20 dm³

• 5 dm³ — Incorrect. This would imply CO is half the oxygen volume, which contradicts the 1:2 ratio.
• 20 dm³ — Correct. Follows the 1:2 O₂:CO volume ratio.
• 15 dm³ — Incorrect. No simple stoichiometric relation gives 1.5× here.
• 10 dm³ — Incorrect. That would match a 1:1 ratio, which is not the case for CO formation.