The liquid hydrocarbon likely to be found in the fraction of crude oil used for domestic cooking is?

Analyze the question

The question asks which liquid hydrocarbon is found in the crude oil fraction used for domestic cooking. Domestic cooking fuel in Nigeria is mainly kerosene (the stove fuel) or cooking gas (LPG). The key word is "liquid", so we need the liquid fraction, which is kerosene.

Concept: Fractional distillation of crude oil

| Fraction | Approx. carbon atoms | State at room temp | Use | |---|---|---|---| | Refinery gas / LPG | C1-C4 (e.g. C3H8) | Gas | Cooking gas | | Petrol (gasoline) | C5-C10 | Liquid | Car fuel | | Kerosene | C10-C16 | Liquid | Stoves, jet fuel, lamps | | Diesel | C15-C20 | Liquid | Diesel engines | | Lubricating oil / wax | C20 and above | Viscous liquid / solid | Lubricants, candles |

Solution

• A. C3H8 (propane): a gas at room temperature, a component of cooking gas, but it is not a liquid. Eliminated.
• B. C5H12 (pentane): a very volatile liquid in the petrol fraction. Not used for cooking. Eliminated.
• C. C13H28 (tridecane): falls in the kerosene range (C10-C16), a liquid used in kerosene stoves. This fits.
• D. C20H42 (eicosane): a waxy solid or heavy oil in the lubricating oil/wax fraction. Eliminated.

Answer: C. C13H28

Exam tip: Remember the order by chain length and boiling point: Gas → Petrol → Kerosene → Diesel → Lubricating oil → Bitumen. Small molecules are gases, medium ones are liquids, and large ones are thick or solid. When a question says "domestic cooking" and "liquid", think kerosene (about C10-C16).