CBSE Class 11 Thermodynamics Worksheet B

Question. A container that suits the occurrence of an isothermal process should be made of:
a. Copper
b. Glass
c. Wood
d. Cloth
Answer : A

Question. When an ideal gas in a cylinder was compressed isothermally by a piston, the work done on the gas was found to be 1.5×10⁴ joules . During this process about:
a. 3 3.6×10³ cal of heat flowed out from the gas
b. 3 3.6×10³ cal of heat flowed into the gas
c. 4 1.5×10³ cal of heat flowed into the gas
d. 4 1.5×10³ cal of heat flowed out from the gas
Answer : A

Question. One mole of O₂ gas having a volume equal to 22.4 litres at 0 ^oC and 1 atmospheric pressure in compressed isothermally so that its volume reduces to 11.2 litres. The work done in this process is:
a. 1672.5 J
b. 1728 J
c. −1728 J
d. –1572.5 J
Answer : D

Question. When 1 gm of water at 0°C and 1×10⁵ N /m² pressure is converted into ice of volume 1.091 cm², the external work done will be:
a. 0.0091 joule
b. 0.0182 joule
c. – 0.0091 joule
d. – 0.0182 joule
Answer : A

Question. One mole of an ideal gas expands at a constant temperature of 300 K from an initial volume of 10 litres to a final volume of 20 litres. The work done in expanding the gas is: (R = 8.31 J/mole-K)
a. 750 joules
b. 1728 joules
c. 1500 joules
d. 3456 joules
Answer : B

Question. An ideal gas is expanded adiabatically at an initial temperature of 300 K so that its volume is doubled. The final temperature of the hydrogen gas is: (γ =1.40)
a. 227.36 K
b. 500.30 K
c. 454.76 K
d. – 47°C
Answer : A

Question. A diatomic gas initially at 18°C is compressed adiabatically to one-eighth of its original volume. The temperature after compression will be:
a. 10°C
b. 887°C
c. 668°K
d. 144°C
Answer : C

Question. An ideal gas at a pressures of 1 atmosphere and temperature of 27°C is compressed adiabatically until its pressure becomes 8 times the initial pressure, then the final temperature is: (γ = 3/2)
a. 627°C
b. 527°C
c. 427°C
d. 327°C
Answer : D

Question. One mole of an ideal gas at an initial temperature of T K does 6 R joules of work adiabatically. If the ratio of specific heats of this gas at constant pressure and at constant volume is 5/3, the final temperature of gas will be:
a. (T + 2.4) K
b. (T − 2.4) K
c. (T + 4)K
d. (T − 4)K
Answer : D

Question. One mole of an ideal gas with γ = 1.4, is adiabatically compressed so that its temperature rises from 27°C to 35°C. The change in the internal energy of the gas is: (R = 8.3 J/mol.K)
a. –166 J
b. 166 J
c. –168 J
d. 168 J
Answer : B

Question. Helium at 27°C has a volume of 8 litres. It is suddenly compressed to a volume of 1 litre. The temperature of the gas will be: [γ = 5 / 3]
a. 108°C
b. 9327°C
c. 1200°C
d. 927°C
Answer : D

Question. When heat in given to a gas in an isobaric process, then:
a. The work is done by the gas
b. Internal energy of the gas increases
c. Both (a) and (b)
d. None from (a) and (b)
Answer : C

Question. Two kg of water is converted into steam by boiling at atmospheric pressure. The volume changes from 2 x 10^-3m3 to 3 3.34m³. The work done by the system is about:
a. – 340 kJ
b. – 170 kJ
c. 170 kJ
d. 340 kJ
Answer : D

Question. How much work to be done in decreasing the volume of and ideal gas by an amount of 2.4 10^-4 m³ at normal temperature and constant normal pressure of 1×10⁵ N /m²
a. 28 joule
b. 27 joule
c. 25 joule
d. 24 joule
Answer : D

Question. Which relation is correct for isometric process?
a. ΔQ = ΔU
b. ΔW = ΔU
c. ΔQ = ΔW
d. None of these
Answer : A

Question. Entropy of a thermodynamic system does not change when this system is used for:
a. Conduction of heat from a hot reservoir to a cold reservoir
b. Conversion of heat into work isobarically
c. Conversion of heat into internal energy isochorically
d. Conversion of work into heat isochorically
Answer : D

Question. Carnot cycle (reversible) of a gas represented by a Pressure-Volume curve is shown in the diagram Consider the following statements:

I. Area ABCD = Work done on the gas
II. Area ABCD = Net heat absorbed
III. Change in the internal energy in cycle = 0
Which of these are correct?
a. I only
b. II only
c. II and III
d. I, II and III
Answer : C

Question. Efficiency of a Carnot engine is 50% when temperature of outlet is 500 K. In order to increase efficiency up to 60% keeping temperature of intake the same what is
temperature of outlet:
a. 200 K
b. 400 K
c. 600 K
d. 800 K
Answer : B

Question. A Carnot engine takes 103 kcal of heat from a reservoir at 627°C and exhausts it to a sink at 27°C. The efficiency of the engine will be:
a. 22.2%
b. 33.3%
c. 44.4%
d. 66.6%
Answer : D

Question. In a Carnot engine, when T₂ = 0°C and T₁ = 200°C, its efficiency is η₁ and when T₁ = 0°C and T₂ = −200°C , Its efficiency is η₂ , then what is η₁ /η₂
a. 0.577
b. 0.733
c. 0.638
d. Can not be calculated
Answer : A

Question. A cyclic process ABCA is shown in the V-T diagram. Process on the P-V diagram is:

Answer : C

Question. In the cyclic process shown in figure, ΔU₁ and ΔU₂ represent the change in internal energy in the process A and B respectively. If ΔQ be the net heat given to the system in the process and ΔW be the net work done by the system in the process, then:

a. ΔU₁ + ΔU₂ = 0
b. ΔU₁ − ΔU₂ = 0
c. ΔQ − ΔW = 0
d. ΔQ + ΔW = 0
Answer : A, C

Question. In the arrangement shown in the figure, gas is thermally insulated.

An ideal gas is filled in the cylinder having pressure P₀ (> atom spheric pressure Pa). The spring of force constant K is initially unstretched. The piston of mass m and area S is frictionless. In equilibrium, the piston rises up a distance x₀, then:
a. final pressure of the gas is P₀ + Kx₀/S + mg/S
b. work done by the gas is 1/2 Kx²₀ + mgx₀
c. decrease in internal energy of the gas is 1/2 Kx²₀ + mgx₀ + P₀Sx₀
d. All of the above
Answer : A, C

Question. A gas undergoes change in its state form position A to position B, via three different paths as shown in the figure.
Select the correct alternatives:

a. Change in internal energy in all the three paths is equal
b. In all the three paths heat is absorbed by the gas
c. Heat absorbed/released by the gas is maximum in path 1
d. Temperature of the gas first increases and then decreases continuously in path (1)
Answer : A, B, C

Question. An ideal gas undergoes a thermodynamic cycle as shown in the figure. Which of the following statements are correct?

a. Straight line AB cannot pass through O
b. During process AB, temperature decreases while during process BC it increases
c. During process BC, work is done by the gas against external process and temperature of the gas increases
d. During process CA, work is done by the gas against external pressure and heat supplied to the gas is exactly equal to this work.
Answer : B, D

Question. The following are one P-V diagrams for the cyclic processes for a gas. In which of these processes is heat absorbed by the gas:

Answer : A, B, C

Question. By what percentage should the pressure of a given mass of a gas be increased so as to decrease its volume by 10% at a constant temperature?
(a) 8.1 %
(b) 9.1 %
(c) 10.1 %
(d) 11.1 %
Answer: D

Question. A refrigerator works between 0ºC and 27ºC. Heat is to be removed from the refrigerated space at the rate of 50 kcal/ minute, the power of the motor of the refrigerator is
(a) 0.346 kW
(b) 3.46 kW
(c) 34.6 kW
(d) 346 kW
Answer: A

Question. Two cylinders fitted with pistons contain equal amount of an ideal diatomic gas at 300 K. The piston of A is free to move, while that of B is held fixed. The same amount of heat is given to the gas in each cylinder. If the rise in temperature of the gas in A is 30 K, then the rise in temperature of gas in B is
(a) 30 K
(b) 18 K
(c) 50 K
(d) 42 K
Answer: D

Question. A Carnot engine works first between 200°C and 0°C and then between 0°C and –200°C. The ratio of its efficiency in the two cases is
(a) 1.0
(b) 0.577
(c) 0.34
(d) 0.68
Answer: B

Question. A perfect gas goes from a state A to another state B by absorbing 8 × 105 J of heat and doing 6.5 × 10⁵ J of external work. It is now transferred between the same two states in another process in which it absorbs 10⁵ J of heat. In the second process
(a) work done by gas is 10⁵ J
(b) work done on gas is 10⁵ J
(c) work done by gas is 0.5 × 10⁵ J
(d) work done on the gas is 0.5 × 10⁵ J
Answer: D

Question. A thermodynamic system is taken through the cycle ABCD as shown in figure. Heat rejected by the gas during the cycle is
(a) 2 PV
(b) 4 PV
(c) 1/2
(d) P V
Answer: A

Question. Which of the following is incorrect regarding first law of thermodynamics?
(a) It is a restatement of principle of conservation of energy.
(b) It is applicable to cyclic processes
(c) It introduces the concept of entropy
(d) It introduces the concept of internal energy
Answer: C

Question. A refrigerator works between 4°C and 30°C. It is required to remove 600 calories of heat every second in order to keep the temperature of the refrigerated space constant. The power required is: (Take 1 cal = 4.2 joules)
(a) 2.365 W
(b) 23.65 W
(c) 236.5 W
(d) 2365 W
Answer: C

Question. A Carnot’s engine works as a refrigerator between 250 K and 300 K. If it receives 750 calories of heat from the reservoir at the lower temperature, the amount of heat rejected at the higher temperature is
(a) 900 calories
(b) 625 calories
(c) 750 calories
(d) 1000 calories
Answer: A

Question. A Carnot engine is working between 127°C and 27°C. The increase in efficiency will be maximum when the temperature of
(a) the source is increased by 50°C
(b) the sink is decreased by 50°C
(c) source is increased by 25°C and that of sink is decreased by 25°C
(d) both source and sink are decreased by 25°C each.
Answer: B

Question. During an adiabatic process an object does 100J of work and its temperature decreases by 5K. During another process it does 25J of work and its temperature decreases by 5K. Its heat capacity for 2^nd process is
(a) 20 J/K
(b) 24 J/K
(c) 15 J/K
(d) 100 J/K
Answer: C

Question. The temperature at which speed of sound in air becomes double of its value at 27° C is
(a) 54°C
(b) 327°C
(c) 927°C
(d) None of these
Answer: C

Question. Air conditioner is based on the principle of
(a) Carnot cycle
(b) refrigerator
(c) first low of thermodynamics
(d) None of these
Answer: B

Question. An ideal refrigerator has a freezer at a temperature of 13ºC. The coefficient of performance of the engine is 5. The temperature of the air (to which heat is rejected) is
(a) 320ºC
(b) 39ºC
(c) 325 K
(d) 325ºC
Answer: B

Question. One mole of an ideal monoatomic gas is heated at a constant pressure of one atmosphere from 0ºC to 100ºC. Then the work done by the gas is
(a) 6.56 joule
(b) 8.32 × 10² joule
(c) 12.48 × 10² joule
(d) 20.8 × 10² joule
Answer: B

Question. During isothermal expansion, the slope of P-V graph
(a) decreases
(b) increases
(c) remains same
(d) may increase or decrease
Answer: A

Question. A carnot’s engine takes 300 calories of heat at 500 K and rejects 150 calories of heat to the sink. The temperature of the sink is
(a) 1000 K
(b) 750 K
(c) 250 K
(d) 125 K
Answer: C

Question. The source and sink temperatures of a Carnot engine are 400 K and 300 K, respectively. What is its efficiency?
(a) 100%
(b) 75%
(c) 33.3%
(d) 25%
Answer: D

Question. A closed gas cylinder is divided into two parts by a piston held tight. The pressure and volume of gas in two parts respectively are (P, 5V) and (10P, V). If now the piston is left free and the system undergoes isothermal process, then the volumes of the gas in two parts respectively are
(a) 2V, 4V
(b) 3V, 3V
(c) 5V, V
(d) 10/11V , 20/11V
Answer: A

1. Draw a p – v diagram for isothermal and adiabatic expansion?

2. State zeroth law of thermodynamics?

3. Can a gas be liquefied at any temperature by increase of pressure alone?

4. A certain gas at atmospheric pressure is compressed adiabatically so that its volume becomes half of its original volume. Calculate the resulting pressure?

5. Why is conversion of heat into work not possible without a sink at lower temperature?

6. Write the sign conventions for the heat and work done during a thermodynamic process?

7. Deduce the work done in the following complete cycle?

8. One kilogram molecule of a gas at 400k expands isothermally until its volume is doubled. Find the amount of work done and heat produced? 

9. Derive the equation of state for adiabatic change?

Click on link below to download CBSE Class 11 Thermodynamics Worksheet B.