WAEC 2015 Chemistry · Question 10

Consider the following reaction equation: C2H4(g) + 3O2(g) 2CO2(g) + 2H2O(g) The volume of CO2(g) produced at…

Question

Consider the following reaction equation: C2H4(g) + 3O2(g) $\to$ 2CO2(g) + 2H2O(g) The volume of CO2(g) produced at s.t.p when 0.05 moles of C2H4(g) was burnt in O2(g) is [Molar Volume of gas = 22.4dm3

A.1.12dm3
B.2.24dm3
C.3.72dm3
D.4.48dm3

Answer: B. 2.24dm3

Explanation written with AI and checked against the answer key

Analyze the question: We need the volume of CO₂ at s.t.p. produced when 0.05 mol of ethene (C₂H₄) burns completely. Concept: Use the mole ratio from the balanced equation, then convert moles to volume using the molar volume (1 mole of any gas at s.t.p. = 22.4 dm³). Solution: Balanced equation: C₂H₄(g) + 3O₂(g) → 2CO₂(g) + 2H₂O(g) Step 1: Mole ratio 1 mole of C₂H₄ produces 2 moles of CO₂. Step 2: Moles of CO₂ produced Moles of CO₂ = 2 × 0.05 = 0.10 mol Step 3: Volume of CO₂ Volume = moles × molar volume Volume = 0.10 × 22.4 = 2.24 dm³ Answer: 2.24 dm³, which is option B. Tip: In gas-volume questions, always follow this path: given moles → mole ratio → moles wanted → × 22.4 dm³. Don't forget the coefficient (here, the 2 in front of CO₂). Forgetting it would give 1.12 dm³ (option A), which is a common trap.

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