Question

The following fuels are burned in excess oxygen at constant pressure and temperature. Arrange these fuels in increasing order of the amount of energy released by them per kilogram on complete combustion.
a,Wood < Coal < Petrol < CNG
b,Coal < Wood < CNG < Petrol
c, Wood < Coal < CNG < Petrol
d,Wood < Petrol < CNG < Coal
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Answer 1

Answer:

C.

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Answer 2

Answer:

The answer is option (a) Wood < Coal < Petrol < CNG

Explanation:

Calorific value is the amount of energy released on complete combustion of 1 kg of fuel. Its unit is  kilojoule per kg(kJ/kg)

• Wood and Coal are examples of solid fuel, which lefts some ash or residue after combustion.

• The calorific value of wood and Coal are 17,000 kJ/kg and 25,000 kJ/kg

• Petrol is an example of Liquid fuel having a calorific value of 45,000kJ/kg

• Whereas, CNG, Biogas, and hydrogen are examples of gaseous fuel.

• The amount of  energy produced by the complete combustion of CNG is 50,000 kJ/kg

So the increasing order of the amount of energy released by wood, coal, CNG, and petrol on combustion is as follows:

                            Wood < Coal < Petrol < CNG