Correct Answer - Option 4 : Kilojoules per kilogram
Explanation:
Calorific value:
- It is the measure of the efficiency of fuel.
- Fuel gives energy by burning (combustion).
- More calorific value, more efficient fuel.
- The amount of heat energy produced on complete combustion of 1 kg of a fuel is called its calorific value.
- If more amount of heat can be generated by using less amount of fuel, we say it have good calorific value.
- It is the amount of energy divided by mass.
- The unit of calorific value can be derived from this.
- Calorific value = Energy / Mass
- So, units can be
\(Unit \ of \ Calorific\ value = \frac{Unit \ of \ energy}{Unit \ of \ mass} \)
- It can be Joule / Kg or Calorie/gram or kJ / Calorie, where joule, calorie, kJ are units of energy and gram and kilograms are units of mass.
- The most general form which is commonly used is Kilojoules per kilogram as fuels are burnt in large amounts.
- Using Kilojoules per kilogram makes things easier.
So, the correct option is Kilojoules per kilogram.
Although, Calories per gram, Kilocalories per kilogram are also units of Calorific value: but here it has been asked about the most commonly used value.
Calorific values of some fuels are given in below table.
| FUEL |
CALORIFIC VALUE (KJ/Kg) |
| Hydrogen |
150000 |
| LPG |
55000 |
| CNG |
50000 |
| Petrol |
45000 |
| Kerosene |
45000 |
| Diesel |
45000 |
| Coal |
25000-33000 |
| Wood |
17000-22000 |
| Cow dung |
6000-8000 |
- Conventional sources such as cow dung, wood, coal, etc are having lower calorific value.
- These fuels are inefficient as compared to LPG and natural gases. Also, they are hazardous to the environment.
