See image — Isomerism and Stereochemistry Chemistry Question

💡 Solution & Explanation

These are all alkanes (saturated hydrocarbons) with the general formula CnH(2n+2). We need to count the number of structural (constitutional) isomers for each. Concept: Structural isomers of alkanes differ in the arrangement of the carbon skeleton (chain isomers and branched isomers). (a) C4H10 — Butane (4 carbons): 1. n-butane: CH3-CH2-CH2-CH3 2. isobutane (2-methylpropane): (CH3)3CH Total = 2 isomers → matches (p) (b) C5H12 — Pentane (5 carbons): 1. n-pentane: CH3CH2CH2CH2CH3 2. isopentane (2-methylbutane): CH3CH(CH3)CH2CH3 3. neopentane (2,2-dimethylpropane): C(CH3)4 Total = 3 isomers → matches (q) (c) C6H14 — Hexane (6 carbons): 1. n-hexane 2. 2-methylpentane 3. 3-methylpentane 4. 2,2-dimethylbutane 5. 2,3-dimethylbutane Total = 5 isomers → matches (r) (d) C7H16 — Heptane (7 carbons): 1. n-heptane 2. 2-methylhexane 3. 3-methylhexane 4. 2,2-dimethylpentane 5. 2,3-dimethylpentane 6. 2,4-dimethylpentane 7. 3,3-dimethylpentane 8. 3-ethylpentane 9. 2,2,3-trimethylbutane Total = 9 isomers → matches (s) Therefore, the correct answer is a-p; b-q; c-r; d-s.