Question

In an experiment 4.5 kg of a fuel was completely burnt. The heat produced was measured to be 1,80,000kJ. Calculate the calorific value of the fuel( in kJ/kg)?

Answer 1

Hint: Calorific value of a fuel means the amount of heat released when 1 g of the fuel undergoes complete combustion in the presence of the excess of oxygen. So, we know the amount of heat produced by 4.5 kg of fuel and from this, we can easily calculate the amount of heat produced by 1 gram of the fuel.

Complete step by step answer:
First of all, let’s discuss the amount of fuels and the calorific value . By the term fuels we mean those substances which burn readily in the presence of the oxygen to produce the heat. Examples of fuels are oil, petroleum, coal etc. and different amounts of heat are released when different types of fuels undergo combustion.
The calorific value of fuel means the amount of heat released when 1gram of the fuel undergoes combustion i.e. when 1gram of the fuel is completely burnt in the presence of excess oxygen. Since, it’s the calorific value of fuel, it is also known as fuel value and its units are kJ/g.
Now, considering the numerical :
As we know that the calorific value is the amount of heat produced when 1 gram of the fuel undergoes combustion.
Heat given by 4.5 kg of fuel is 1,80,000kJ (given) i.e.
4.5 kg of the fuel produces = 180000 kJ of heat
Then,
1kg of the fuel produces = $\dfrac{180000}{4.5}$ kJ of heat
                                      =40,000kJ of heat
Hence, the calorific value of the fuel is 40,000kJ.

Note: The fuels which have higher fuel values or calorific values occupy large volume and have low values for the density and vice- versa. Since, the fuels on combustion produce large amounts of heat, hence the fuel value or calorific value is also called as the heat value.