Understanding Calorific Value

Calorific value is the amount of heat energy produced when a unit mass (or volume) of a fuel is completely burned. It is measured in kilojoules per kilogram (kJ/kg) or kilocalories per kilogram (kcal/kg). Fuels with higher calorific values release more energy per unit mass.

Step 1: Compare Common Fuels

Different fuels have different calorific values due to their chemical composition. Hydrocarbon fuels with higher hydrogen content and lower impurities generally have higher calorific values.

Step 2: Recall Typical Calorific Values

Here are approximate calorific values for the given options:

• Petrol: ~45,000 kJ/kg
• Biogas: ~35,000-40,000 kJ/m³ (lower than others due to CO₂ content)
• Kerosene: ~46,000 kJ/kg
• LPG (Liquefied Petroleum Gas): ~46,000-50,000 kJ/kg

Step 3: Identify the Highest

Among these, LPG typically has the highest calorific value. It is a mixture of propane and butane, which are efficient hydrocarbons with high energy content per unit mass.

Final Answer

LPG has the highest calorific value among the given options.

Related Topics

• Fuel Efficiency: How well a fuel converts chemical energy to usable energy.
• Combustion: The chemical process of burning fuels, producing heat and light.
• Energy Content: Measurement of energy stored in fuels, important for comparing energy sources.

Formulae and Theory

Calorific value (CV) is calculated using:

Units: kJ/kg or kcal/kg.

Theoretical calorific value can be derived from the heat of combustion for pure hydrocarbons. For example, methane (main component of natural gas) has a high calorific value of about 55,000 kJ/kg.