Which of the following fuels show highest calorific value?

Concept: The calorific value of a fuel is the amount of heat released when a unit mass (per kilogram) of that fuel undergoes complete combustion. It depends chiefly on a fuel's elemental composition — combustion converts the fuel's carbon to CO2 and its hydrogen to H2O, and per unit mass, oxidizing hydrogen releases substantially more heat than oxidizing carbon. So a fuel with a higher hydrogen-to-carbon mass ratio (typically the lighter, more volatile hydrocarbon fractions) yields a higher calorific value per kilogram than a heavier, more carbon-rich hydrocarbon fraction.

Application: Among common refined liquid fuels, Petrol (gasoline) is the lightest and most volatile fraction of crude oil, followed by Kerosene, with Diesel being the heaviest and densest of the three. Standard reference values (e.g. IPCC 2006 Guidelines for National Greenhouse Gas Inventories, and engineering fuel-data tables) place Petrol at roughly 45-48 MJ/kg (~11,950 kcal/kg), Kerosene at roughly 43-46 MJ/kg (~10,500 kcal/kg), and Diesel at roughly 42-45 MJ/kg (~10,000 kcal/kg). Petrol's lighter, more hydrogen-rich composition gives it the highest calorific value per kilogram of the three.

Cross-check: This ranking is corroborated independently by international emission-factor standards (IPCC) and engineering energy-content references, which both place gasoline/petrol marginally above kerosene and diesel on a per-kilogram basis. Checking each alternative confirms Petrol as the single correct choice:

• Diesel's heavier, denser hydrocarbon composition gives it strong energy content per litre (volumetric density), but a lower energy content per kilogram than the lighter fuels compared here.

• Kerosene sits between diesel and petrol in both refining cut and calorific value — energy-dense, but not the top value in this comparison.

• The three values are close in magnitude but are not identical in standard reference tables, so more than one option cannot simultaneously hold the single highest value.

• Since one of the three named fuels does hold the top value in standard references, the correct choice is not absent from the given options.