Q1. [2] § 4.3 CHEMICAL PROPERTIES OF CARBON COMPOUNDS § 4.3.3 Addition Reaction
Distinguish between a saturated and an unsaturated hydrocarbon by flame test. List the products of combustion reaction of a saturated hydrocarbon.
Previously asked in CBSE board exam
2024 31/4/1 Q22
Generated by claude-sonnet-4-6 · 2026-06-15 06:47 · grounding rag
Model Answer
Flame test:
Saturated hydrocarbons burn with a blue, non-sooty flame, while unsaturated hydrocarbons burn with a yellow, sooty (smoky) flame.
Products of combustion of a saturated hydrocarbon:
Carbon dioxide (CO₂) and water (H₂O) are produced.
Example: CH₄ + 2O₂ → CO₂ + 2H₂O
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Explanation
- The flame test is the key distinguishing test: soot/smokiness indicates unsaturation (higher carbon-to-hydrogen ratio causes incomplete combustion).
- Examiners expect both parts answered: (1) the distinction and (2) the products.
- Writing the equation for methane combustion earns full credit and shows understanding. Keep it concise — no extra explanation needed for 2 marks.
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