The correct option is (a) 1 only.
Explanation
The efficiency of a fuel is determined by its calorific value, which is defined as the amount of heat energy produced on the complete combustion of 1 kilogram of a fuel. It is expressed in units of kilojoules per kilogram (kJ/kg). A higher calorific value indicates a more efficient fuel.
Statement-wise Analysis:
- Statement 1 is Correct: Liquefied Petroleum Gas (LPG) has a significantly higher calorific value compared to wood. The calorific value of LPG is approximately 55,000 kJ/kg, whereas wood typically ranges between 17,000 and 22,000 kJ/kg. Consequently, LPG produces more heat per unit mass than wood.
- Statement 2 is Incorrect: Cow dung cake has one of the lowest calorific values among common solid fuels, ranging from 6,000 to 8,000 kJ/kg. In contrast, coal has a much higher calorific value, typically ranging from 25,000 to 33,000 kJ/kg depending on the variety (e.g., anthracite, bituminous). Therefore, coal is a more energy-dense fuel than cow dung cake.
Key Takeaway:
Gaseous fuels (like Hydrogen and LPG) generally possess higher calorific values than liquid fuels (like Kerosene and Petrol), which in turn have higher values than solid fuels (like Wood, Coal, and Cow dung cakes). Hydrogen has the highest calorific value (~150,000 kJ/kg).