See image — Hydrocarbons Chemistry Question

💡 Solution & Explanation

Concept: Catalytic hydrogenation (H2/Pt) adds H2 across a C=C double bond, converting an alkene to an alkane. To give n-butane (CH3CH2CH2CH3), the alkene must have a straight 4-carbon chain (no branching) and contain a C=C double bond somewhere along that chain. Step 1: Identify all alkenes with molecular formula C4H8 that have a straight (n-butyl) carbon skeleton. - 1-Butene: CH2=CHCH2CH3 → hydrogenation gives CH3CH2CH2CH3 (n-butane) ✓ - 2-Butene (cis or trans): CH3CH=CHCH3 → hydrogenation gives CH3CH2CH2CH3 (n-butane) ✓ Note: cis-2-butene and trans-2-butene are counted as separate alkenes, both giving n-butane ✓ - Isobutylene (2-methylpropene): CH2=C(CH3)2 → hydrogenation gives (CH3)2CHCH3 = isobutane, NOT n-butane ✗ Step 2: Count the alkenes giving n-butane: 1. 1-Butene 2. cis-2-Butene 3. trans-2-Butene Total = 3 alkenes Step 3: Why other options fail: - Option (a) 1: Incorrect, there are more than one. - Option (b) 2: Incorrect, cis and trans 2-butene are distinct and both must be counted along with 1-butene. - Option (d) 4: Incorrect, isobutylene gives isobutane, not n-butane, so only 3 qualify. Therefore, the correct answer is C.