Correct Option
The correct option is (a).
Explanation
A fuel is a substance that reacts with oxygen to release energy, typically in the form of heat. The suitability of a fuel is determined by its calorific value, ignition temperature, availability, cost, and the nature of combustion (rate and by-products).
Statement-wise Analysis
- Statement 1 is Correct: A "good" fuel is defined by practical utility. It must be readily available, cheap, and easy to transport and store. Additionally, it should have a high calorific value and leave minimal undesirable residue.
- Statement 2 is Incorrect: An ideal fuel should burn in air at a moderate rate. Explosive combustion implies an uncontrolled release of energy, which is dangerous and inefficient for standard heating or engine applications. Controlled combustion is a prerequisite for a fuel to be considered ideal or good.
- Statement 3 is Incorrect: While Compressed Natural Gas (CNG) is an excellent fuel due to its low pollution levels and high calorific value, it is not an ideal fuel in all respects. In scientific terms, an ideal fuel is a theoretical concept; no known fuel satisfies every single requirement (such as zero cost, infinite availability, zero pollution, and perfect transportability) simultaneously. CNG, for instance, requires heavy cylinders for storage and has specific infrastructure requirements.
Key Takeaway: An ideal fuel is a theoretical standard that does not exist in reality. A good fuel is one that is cheap, readily available, burns at a moderate rate, and produces a large amount of heat without leaving significant residue.