Solving the Thermodynamics Multiple Choice Questions of Class 11 Physics Chapter 12 MCQ can be of extreme help as you will be aware of all the concepts. These MCQ Questions on Thermodynamics Class 11 with answers pave for a quick revision of the Chapter thereby helping you to enhance subject knowledge. Have a glance at the MCQ of Chapter 12 Physics Class 11 and cross-check your answers during preparation.

Question 1.
A vessel contains a mixture of one mole of oxygen and two moles of nitrogen at 300 K. The ratio of the average rotational kinetic energy per O² to per N² molecule is
(a) 1 : 1
(b) 1 : 2
(c) 2 : 1
(d) depends on the moment of inertia of the two molecules

Answer

Answer: (a) 1 : 1

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Question 2.
For a diatomic gas change in internal energy for a unit change in temperature for constant pressure and constant volume is U1 and U2 respectively. What is the ratio of U1 and U2?
(a) 5 : 3
(b) 3 : 5
(c) 1 : 1
(d) 5 : 7

Answer

Answer: (c) 1 : 1

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Question 3.
An ideal gas heat engine operates in Carnot cycle between 227°C and 127°C. It absorbs 6 × 104 cal of heat at higher temperature. Amount of heat converted to work is:
(a) 2.4 × 104 cal
(b) 6 × 104 cal
(c) 1.2 × 104 cal
(d) 4.8 × 104 cal

Answer

Answer: (c) 1.2 × 104 cal

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Question 4.
Which of the following parameters dose not characterize the thermodynamic state of matter?
(a) work
(b) volume
(c) pressure
(d) temperature

Answer

Answer: (a) work

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Question 5.
A Carnot engine whose sink is at 300 K has an efficiency of 40%. By how much should the temperature of source be increased, so as to increase its efficiency by 50% of original efficiency?
(a) 275 K
(b) 325 K
(c) 250 K
(d) 380 K

Answer

Answer: (c) 250 K

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Question 6.
The translational kinetic energy of gas molecules at temperature T for one mole of a gas is
(a) (3/2) RT
(b) (9/2) RT
(c) (1/3) RT
(d) (5/2) RT

Answer

Answer: (a) (3/2) RT

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Question 7.
The temperature of reservoir of Carnots engine operating with an efficiency of 70% is 1000 kelvin. The temperature of its sink is
(a) 300 K
(b) 400 K
(c) 500 K
(d) 700 K

Answer

Answer: (a) 300 K

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Question 8.
A gas is taken through a number of thermodynamic states. What happens to its specific heat?
(a) It is always constant.
(b) It increases.
(c) It decreases.
(d) It can have any value depending upon the process of heat absorbed or evolved.

Answer

Answer: (d) It can have any value depending upon the process of heat absorbed or evolved.

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Question 9.
Directions: The following question has four choices out of which ONLY ONE is correct. A refrigerator with its power on, is kept in a closed room with its door open, then the temperature of the room will _________.
(a) rise
(b) fall
(c) remain the same
(d) depend on the area of the room

Answer

Answer: (a) rise

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Question 10.
Directions: The following question has four choices out of which ONLY ONE is correct. Which of the following is incorrect regarding the first law of thermodynamics? A. It is not applicable to any cyclic process B. It is a restatement of the principle of conservation of energy C. It introduces the concept of the internal energy D. It introduces the concept of the entropy
(a) A and D
(b) B and C
(c) C and A
(d) A and B

Answer

Answer: (a) A and D

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Question 11.
For a diatomic gas change in internal energy for a unit change in temperature for constant pressure and constant volume is U1 and U2 respectively. What is the ratio of U1 and U2?
(a) 5 : 3
(b) 3 : 5
(c) 1 : 1
(d) 5 : 7

Answer

Answer: (c) 1 : 1

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Question 12.
An engine has an efficiency of 1/6. When the temperature of sink is reduced by 62°C, its efficiency is doubled. Temperature of the source is:
(a) 124°C
(b) 37°C
(c) 62°C
(d) 99°C

Answer

Answer: (d) 99°C

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Question 13.
Directions: The following question has four choices out of which ONLY ONE is correct. A Carnots 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 cal
(b) 625 cal
(c) 750 cal
(d) 1000 cal

Answer

Answer: (a) 900 cal

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Question 14.
An ideal gas heat engine operates in a Carnot cycle between 227°C and 127°C. It absorbs 6 kcal at the higher temperature. The amount of heat (in kcal) converted into work is equal to:
(a) 1.6
(b) 1.2
(c) 4.8
(d) 3.5

Answer

Answer: (b) 1.2

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Question 15.
A vessel contains a mixture of one mole of oxygen and two moles of nitrogen at 300 K. The ratio of the average rotational kinetic energy per O² to per N² molecule is
(a) 1 : 1
(b) 1 : 2
(c) 2 : 1
(d) depends on the moment of inertia of the two molecules

Answer

Answer: (a) 1 : 1

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Question 16.
Which of the following statements is correct for any thermodynamic system?
(a) The internal energy changes in all processes.
(b) Internal energy and entropy are state functions.
(c) The change in entropy can never be zero.
(d) The work done in an adiabatic process is always zero.

Answer

Answer: (b) Internal energy and entropy are state functions.

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Question 17.
The temperature of reservoir of Carnots engine operating with an efficiency of 70% is 1000 kelvin. The temperature of its sink is
(a) 300 K
(b) 400 K
(c) 500 K
(d) 700 K

Answer

Answer: (a) 300 K

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Question 18.
Directions: The following question has four choices out of which ONLY ONE is correct. Which of the following is incorrect regarding the first law of thermodynamics? A. It is not applicable to any cyclic process B. It is a restatement of the principle of conservation of energy C. It introduces the concept of the internal energy D. It introduces the concept of the entropy
(a) A and D
(b) B and C
(c) C and A
(d) A and B

Answer

Answer: (a) A and D

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Question 19.
A black body at a temperature of 227°C radiates heat at the rate of 20 cal m^-2s-1. When its temperature rises to 727°C, the heat radiated will be
(a) 40 units
(b) 160 units
(c) 320 units
(d) 640 units

Answer

Answer: (c) 320 units

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Question 20.
At a given volume and temperature, the pressure of a gas
(a) varies inversely as its mass
(b) varies inversely as the square of its mass
(c) varies linearly as its mass
(d) is independent of its mass

Answer

Answer: (c) varies linearly as its mass

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