Stoichiometry of alkane combustion and ideal gas law

Steps:

• Combustion of alkane CₓH₂ₓ₊₂ produces x moles CO₂ per mole of alkane.
• For 2 moles of alkane, total moles CO₂ produced = 2x.
• Apply ideal gas law to find moles of CO₂: n = (P × V) / (R × T).
• Substituting values (P = 1.01 × 10⁵ Pa, V = 0.0004 m³, R = 8.314 Pa m³ mol⁻¹ K⁻¹, T = 301 K) yields n = 8 mol, so 2x = 8 and x = 4.

Why A is correct:

• C₄H₁₀ contains 4 carbon atoms, matching x = 4 from the moles of CO₂ produced.

Why the others are wrong:

• B. C₅H₁₂ requires 10 moles CO₂ from 2 moles alkane, exceeding 8 moles produced.
• C. C₆H₁₄ requires 12 moles CO₂ from 2 moles alkane.
• D. C₇H₁₆ requires 14 moles CO₂ from 2 moles alkane.

Final answer: A