Free First Law of Thermodynamics MCQs with Answers
297 First Law of Thermodynamics MCQs from Physics, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
The first law relates heat supplied, work done and the change in internal energy through energy conservation. Problems use sign conventions and apply the law to isothermal, adiabatic, isobaric and isochoric processes. Internal energy is a state function, while heat and work depend on the path followed.
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297 questions · page 5 of 15
- A. Internal energy
- B. Enthalpy
- C. Entropy
- D. Temperature
- E. Pressure
Explanation: At constant volume, the heat of the reaction is equal to the change in the internal energy of the system.
Correct answer: Internal energy- A. 5 J
- B. 10 J
- C. 20 J
- D. 30 J
- E. 40 J
Explanation: To determine the change in internal energy, apply the first law of thermodynamics: ΔU = Q - W, where ΔU is the change in internal energy…
Correct answer: 10 J- A. Fallen, since more molecules bombarded the container and so they must be moving slower
- B. Fallen, since more molecules collide more frequently with one another and so their average speed is lower
- C. Remains constant if the compression is very slow
- D. Risen, since doing work on the gas increases the kinetic energy of the molecules
- E. Risen, since there are more intermolecular collisions and so more heat is produced by them
Explanation: If an ideal gas is compressed adiabatically, its temperature rises because the heat produced cannot be lost to the surroundings.
Correct answer: Risen, since doing work on the gas increases the kinetic energy of the molecules- A. ΔQ
- B. CV
- C. ΔT
- D. P
- E. ΔV
Explanation: Boyle's Law states that when the temperature of a given mass of confined gas is constant, the product of its pressure and volume is also…
Correct answer: ΔT- A. Isothermal
- B. Adiabatic
- C. Isobaric
- D. Isochoric
Explanation: The rapid escape of air from a burst tyre is an example of an adiabatic process.
Correct answer: Adiabatic- A. The temperature of the sink is 0°C.
- B. The temperature of the sink is 0 K.
- C. The temperature of the source is 0.
- D. The temperature of the sink is equal to the temperature of the source.
Explanation: A frictionless heat engine(Carnot engine) has the following formula for efficiency: Maximum efficiency n = 1 Tc/Th where Th is the…
Correct answer: The temperature of the sink is 0 K.- A. Heat flows out of the system
- B. Work is done by the system
- C. Work is done by the surroundings
- D. The potential energy of the system is changing
Explanation: According to the first law of thermodynamics, Q = ΔU + W, where Q is the heat added to the system, ΔU is the change in internal energy…
Correct answer: Work is done by the system- A. 0.4
- B. 0.5
- C. 0.3
- D. 0.2
Explanation: The percentage of heat utilized is 40% or 0.4.
Correct answer: 0.4- A. ΔH= qv+ w
- B. ΔE=(q)v
- C. ΔH=(q)v
- D. ΔE=(q)v + PV
Explanation: Since we have a constant volume, it is safe to assume that no work is being done on the system, or by the system.
Correct answer: ΔE=(q)v- A. Q = ΔU + W
- B. Q + ΔU = W
- C. Q = ΔU x W
- D. None of these
Explanation: The first law of thermodynamics states that the change in internal energy of a system equals the net heat transfer into the system minus…
Correct answer: Q = ΔU + W- A. CpΔT = CvΔT + PΔV
- B. CvΔT = CpΔT + PΔV
- C. CpΔT = CvΔT + VΔP
- D. ΔCpT = ΔCvT + PΔV
Explanation: Heat supplied to the gas at constant pressure isΔQ=nCPΔTChange in internal energy,ΔU=nCVΔTChange in work done,ΔW = PΔVAccording to the…
Correct answer: CpΔT = CvΔT + PΔV- A. Newton's law
- B. Charles's law
- C. Conservation of energy
- D. Conservation of entropy
Explanation: First law of thermodynamics states that change in internal energy of the system is equal to heat transferred to the system and work done…
Correct answer: Conservation of energy- A. Work done by the system = decrease in internal energy of the system
- B. Work done by the system = increase in internal energy of the system
- C. Work done on the system = decrease in internal energy of the system
- D. Work done on the system = decrease in internal energy of the system + heat released
Explanation: In an adiabatic process, we have no heat exchange thus the internal energy would be depending, solely, upon the work done, either on the…
Correct answer: Work done by the system = decrease in internal energy of the system- A. 0 kJ
- B. 10 kJ
- C. 20 kJ
- D. 30 kJ
Explanation: Heat energy supplied to the Ideal gas = I2RtHeat energy supplied to the Ideal gas = 12x100x5x60Heat energy supplied to the Ideal gas =…
Correct answer: 30 kJ- A. -190
- B. 190
- C. 90
- D. -90
Explanation: In thermodynamics, heat entering the system is taking as positive, and heat leaving the system is taken as negative.Similarly, work done…
Correct answer: -190- A. -190 kJ
- B. 190 kJ
- C. -90 kJ
- D. 90 kJ
Explanation: According to the first law of thermodynamics, if a system absorbs 140 kJ of heat energy (Q) and uses 50 kJ to do work (W) on its…
Correct answer: 90 kJ- A. Q = ΔW/V
- B. W = -Q
- C. W = -ΔU
- D. Q = ΔU
Explanation: In an adiabatic system, there is no heat exchange between the system and its environment so Q = 0.
Correct answer: W = -ΔU- A. L
- B. Zero
- C. L- P(V2-V1)
- D. P(V2-V1)
Explanation: According to the first law of thermodynamics,∆U= Q - W -------- (1)where ∆U is change in internal energyQ is heatand W is work doneSince…
Correct answer: L- P(V2-V1)- A. Enthalpy
- B. Work
- C. Entropy
- D. Heat
Explanation: As the first law of thermodynamics is given byΔU = ΔQ - ΔWwhere ΔU is the change in internal energyΔQ is the heat addedand ΔW is the work…
Correct answer: Heat- A. ∆H=q + w
- B. ∆H= qw
- C. ∆H=q - ∆P∆V
- D. ∆E = q + w
Explanation: The first law of thermodynamics states that energy can neither be created nor be destroyed, but can change from one form to another.
Correct answer: ∆E = q + w