Calorific Value and Efficiency of a Fuel

Q. Question 11
In an experiment, 4.5 kg of a fuel was completely burnt. The heat produced was measured to be 180, 000 kJ. Calculate the calorific value of the fuel.

Q.

(a) Define the calorific value of a fuel.

(b) "The calorific value of LPG is 55000 kJ/kg". What does it mean ?

Q.

Differentiate between complete and incomplete combustion. [3 MARKS]

Q. What is meant by incomplete combustion?

1. Combustion in sufficient supply of water vapour
2. Combustion in sufficient supply of oxygen
3. Combustion in insufficient supply of air
4. Combustion in insufficient supply of carbon dioxide

Q.

What is a good fuel?

Q. What is incomplete combustion? What are it's by-product?

Q. The calorific values of petrol and CNG are 45000 kJ/kg and 50, 000 kJ/kg, respectively. If you have a vehicle which can run on petrol as well as CNG, which fuel will you prefer and why?​

Q. Question 5
The substance that does not burn with flame is

(a) LPG
(b) Dry Grass
(c) Camphor
(d) Charcoal

Q.

Name the unit in which the calorific value of a fuel is expressed.

Q.

Write any four characteristics of an ideal fuel

Q.

Why don, t we use hydrogen as a fuel?

Q.

What is slow combustion?

Q.

Calorific value is expressed in a unit called kilojoule per kg (kJ/kg).

1. True

2. False

Q.

Which of the following fuels has the highest calorific value ?

Kerosene, Wood, Hydrogen, Cow-dung cakes, LPG

Q.

Inflammable substances have

1. Low ignition temperature

2. High ignition temperature

3. No ignition temperature

4. Moderate ignition temperature

Q.

Kerosene is commonly used to start a fire in the wood Give Reason

Q.

Give a reason for the following.

Hydrogen is used as fuel in space rockets.

Q.

What do you understand by fuel efficiency?

Q.

The calorific value of a fuel is 40000 kJ/kg. This fuel is most likely to be :

(a) biogas

(b) methane

(c) hydrogen gas

(d) liquefied petroleum gas

Q.

Combustion of a fuel is an exothermic reaction. True/False

1. True

2. False

Q. Question 26
Fill in the blanks using the words given in the box.

(a) A chemical process in which a substance reacts with oxygen to give off heat is called ___
(b) Wood, paper, CNG are ___ substances.
(c) The lowest temperature at which a substance catches fire is called its ___ temperature.
(d) Ignition temperature of ___ is lower than that of wood.
(e) The substances which have very low ___ temperature and can easily catch fire with a flame are called ___ substances.
(f) The amount of heat energy produced on complete combustion of 1kg of a fuel is called its ___.

Q.

Which of the following fuels has the lowest calorific value ?

(a) kerosene

(b) CNG

(c) biogas

(d) LPG

Q.

Name the term which is used to express the efficiency of a fuel.

Q.

The efficiency of a fuel is expressed in terms of its ________.

1. calorific value
2. density
3. purity
4. volume

Q.

Write the advantages of using LPG as fuel

Q.

Is CNG really pollution free? Why or why not?

Q.

Which of the following is correct with respect to calorific value?

1. It is the amount of heat energy produced on complete combustion of 1 kg of fuel.

2. It is the amount of heat energy produced on complete combustion of 1g of fuel.

3. It is the amount of heat energy required for complete combustion of 1 kg of fuel.

4. It is the amount of heat energy produced on complete combustion of 100 kg of fuel.

Q.

Which of the following fuels has the highest calorific value ?

(a) natural gas

(b) liquefied petroleum gas

(c) coal gas

(d) hydrogen gas

Q.

Choose the incorrect statement from the following. A good fuel is one which-

1. is readily available

2. produces a large amount of heat

3. leaves behind many undesirable substances

4. burns easily in the air at a moderate rate

Q. ___ combustion is a reaction in which a large amount of heat and light are produced in a very short time.