See image — Aromatic Hydrocarbons Chemistry Question

💡 Solution & Explanation

Step 1 - Identify compound X: Heating coke (carbon) with lime (CaO) at high temperature produces calcium carbide (CaC2). This is compound X. Reaction: CaO + 3C -> CaC2 + CO Step 2 - Identify compound Y: Calcium carbide (X) reacts with water to give acetylene (ethyne, HC≡CH). This is compound Y. Reaction: CaC2 + 2H2O -> Ca(OH)2 + HC≡CH Step 3 - Identify compound Z: Acetylene (Y) when passed over red-hot iron (Fe catalyst) at 873 K undergoes trimerization (cyclic polymerization) to form benzene. This is compound Z. Reaction: 3 HC≡CH --(Fe, 873K)--> C6H6 (benzene) Step 4 - Match with options: Benzene is shown in option (a) as the aromatic ring structure. Why other options fail: - Option (b) penta-1,3-diene would require different starting materials and reaction conditions. - Option (c) 1,3-butadiene is not formed by trimerization of acetylene. - Option (d) cyclohexane is a saturated ring, not formed by trimerization of acetylene under these conditions. Therefore, the correct answer is A.