Calorific Value and Efficiency of a Fuel

Q.

Give examples where chemical energy is converted into light energy and heat energy.

Q.

What is S.I unit of calorific value?

Q.

What are the disadvantage of burning cow dung directly as a fuel?

Q.

Liquid hydrogen is used as a rocket fuel.

1. True
2. False

Q.

Statement 1: Combustion or burning takes place only in the presence of oxygen.

Statement 2: Oxygen is a supporter of combustion.

1. Statements (1) and (2) are true.

2. Statement (1) is true and statement (2) is false.

3. Statements (1) and (2) are false.

4. Statement (1) is false, and statement (2) is true.

Q.

The quality of fuel depends on its___value.

Q. The gross calorific value of protein is_______________ kcal/g

1. 4.1
2. 5.65
3. 9.45
4. 9

Q.

Fuels used in rockets are called _____________.

Q.

Discuss the application of cryogenics in space science.

Q.

Why is CNG considered an environmental-friendly fuel? State two reasons for it.

Q.

14. ________ is used as a rocket fuel.

Q. Sort the following in the increasing order of calorific value.

1. Wood
2. Coal
3. LPG
4. Hydrogen

Q.

Which of the following given fuels can be considered as the most efficient fuel based on the calorific value?

1. CNG having calorific value 50000 kJ/kg

2. Petrol having calorific value 45000 kJ/kg

3. Methane having calorific value 50000 kJ/kg

4. Hydrogen having calorific value 150000 kJ/kg

Q. Which of the following is the correct formula for calculating total heat produced $\left(H\right)$ in combustion?
Calorific value $=C$
Mass of substance $=M$

1. $H=C\times M$
2. $H=C÷M$
3. $H=C+M$
4. $H=C-M$

Q. "A fuel has calorific value of $25,000kJ/kg$."
What does the above statement represent?

1. $4kg$ of fuel will release $1,00,000kJ$ energy on combustion.
2. $1kg$ of fuel will release $1,00,000kJ$ energy on combustion.
3. $1kg$ of fuel will take $25,000kJ$ energy on combustion.
4. $4kg$ of fuel will take $1,00,000kJ$ energy on combustion.

Q. Mention any two ways in which cow dung can be utilised as a fuel. Out of two which is better? Justify. (2 marks)
Ans. Cow dung can be used by burning cowdung itself or by burning biogas produced from it. Biogas is more efficient as it's thermal efficiency is higher than that of cow dung. It doesnt contain moisture while cow dung has a lot.
(I got only 1 out of 2 marks)
What should I add?

Q. (a) The calorific value of hydrogen is $150000$ $kJ/kg$. What does this mean?
(b) Even though the calorific value of hydrogen is very high, it is not used as a household fuel. Why?
(c) Give a situation in which this fuel is used.

Q. The combustion of 5.0 g of coke raised the temperature of 1.0g of water from ${10}^{\circ }C$ to ${55}^{\circ }C$. If specific heat of water of 1cal/ g, the calorific value of coke is ......

Q. The correct order for fuels mentioned below in terms of increasing Calorific Value is:
CNG, Petrol, Cow Dung Cake and Wood.

1. Cow Dung Cake > Petrol > Wood > CNG
2. Cow Dung Cake < Petrol < Wood < CNG
3. Cow Dung Cake < Wood < Petrol < CNG
4. Cow Dung Cake < Wood < CNG < Petrol

Q.

Burning of fuels produce …………(oxygen/carbon dioxide).

Q. Which fuel has the highest calorific value?

1. Hydrogen gas
2. Wood
3. Petrol
4. Methane

Q.

Wobbe Index is a characteristic of ____________.

1. Solid fuels

2. Gaseous fuels

3. Liquid fuels

4. Fat coals

Q.

Combustion of saturated hydrocarbons produces ___ and ___ along with heat and light.

Q.

Choose the quantity of fuel from the given options which will produce more heat (Calorific value of 1 kg of Z is 50, 000 kJ/kg).

1. 5 kg

2. 2 kg

3. 4 kg

4. 3 kg

Q.

The …………. given out during combustion is used to generate electricity

Q. Kavita wrote two sentences about calorific value of fuels.
(i)The amount of heat energy required by $1kg$ of a fuel to reach its ignition temperature for the complete combustion is called its calorific value.
(ii)It is expressed in a unit called kilojoule per kg $\left(kJ/kg\right)$.
Choose the correct sentence(s).

1. (i)
2. (ii)
3. Both (i) and (ii)
4. None of these

Q. What is a calorific value of a fuel $2$. Write any four characteristics of an idea fuel?

Q.

List various fields where cryogenics can be used. Also, explain in brief how it finds its application.

Q.

Which of the following statement regarding combustion of fuel is not true?

1. Fuels burn with the help of oxygen.

2. Rate of combustion increases if supply of oxygen is less.

3. Carbon-dioxide is formed during complete combustion.

4. Soot is formed during partial combustion.

Q. Consider the following chemical equation for the combustion of methane.
$C{H}_4+O_2\to C{O}_2+H_{2}O$

1. Energy required to break bonds between C and H in $C{H}_4$ is less than the energy required to form them.
2. Energy required to break bonds between C and H in $C{H}_4$ is more than the energy required to form them.
3. Reactants have more energy than the products.
4. Products have more energy than the reactants.