a) The calorific values of petrol and CNG are 45000 kJ/kg and 50,000 kJ/kg, respectively. Ifyou have vehicle which can run on petrol as well as CNG, which fuel will you prefer andwhy?b) Define calorific value.60 kg of fuel was completely burnt for an experiment. The amount ofheat energy was found to be 1,80,000 kJ. Calculate the calorific value of the fuel.22) (a) Make a labelled diagram of a candle flame.(b) What makes the middle zone of a candle flame luminous?

a) Given the calorific values of petrol and CNG, it would be more efficient to use CNG as a fuel. This is because the calorific value of CNG is higher than that of petrol, meaning that CNG can produce more heat energy per kilogram than petrol. Therefore, a vehicle running on CNG would be more fuel-efficient than one running on petrol.

b) The calorific value of a fuel is the amount of heat energy produced when a certain amount of that fuel is completely burned. It is usually measured in kilojoules per kilogram (kJ/kg).

To calculate the calorific value of the fuel used in the experiment, we would divide the total amount of heat energy produced by the total amount of fuel burned. In this case, that would be 1,80,000 kJ divided by 60 kg, which equals 3000 kJ/kg. Therefore, the calorific value of the fuel used in the experiment is 3000 kJ/kg.

22. a) A labelled diagram of a candle flame would include the following parts: the wick, the fuel (wax), the blue zone (where complete combustion occurs), the dark zone (where no combustion occurs), and the yellow zone (where partial combustion occurs).

b) The middle zone of a candle flame is luminous because it is the area where incomplete combustion occurs. In this zone, there is not enough oxygen for the fuel to burn completely. This incomplete combustion produces tiny particles of soot, which glow when they are heated, making the middle zone of the flame luminous.