Questions on Second Law of Thermodynamics with Answers

Practice Questions on Second Law of Thermodynamics with Answers.

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Questions on Second Law of Thermodynamics with Answers


Q1. A thermally ‘insulated box of volume 2V has a partition which divides it into two chambers of equal volume. Each chamber contains He gas at temperature T and pressure P. On removing the partition, the molecules in the two chambers mix with each other. The change in entropy of the system is

  • (a) –PV/T ln2
  • (b) 0
  • (c) PV/T ln2
  • (d) 2PV/T ln2

Q2. Which of the following statements is correct?

  • (a) a) You can construct an engine operating in cycles, extracting heat Q and performing exactly equivalent work W.
  • (b) You can construct an engine operating in cycles extracting heat Q and performing more than equivalent amount of work W.
  • (c) You can have an engine operating cyclically such that the entropy remains constant throughout the cycle.
  • (d) You cannot construct a cyclically operating engine that will extract heat Q and perform exactly equivalent amount of work W.

Q3. The sole effect of a hypothetical thermodynamic process E1 is to convert an amount Q of heat entirely into work. A second hypothetical process E2 converts an amount W of work entirely into heat. It can be said that the second law of thermodynamics is violated by

  • (a) E1 but not E2
  • (b) E2 but not E1
  • (c) Both E1 and E2
  • (d) neither processes

Q4. Which of the following is true?

  • (a) In an engine the magnitude of entropy change is larger of the source than at the sink
  • (b) When two gases at identical temperature and pressure are mixed, the entropy remains unchanged
  • (c) The only case where entropy of the universe stays constant is in the ideal Carnot’s engine
  • (d) The efficiency of a refrigerator is more in winters than in summers, assuming that the inside temperature attained in the refrigerator is the same in both cases.

Q5. The internal energy of a system is expressed by function U(S,V) = S4/3 Vα , where α is a constant. The value of α is

  • (a) 1
  • (b) 1/3
  • (c) – 1/3
  • (d) 3/4

Q6. The value of entropy at absolute zero of temperature would be

  • (a) Zero for all the materials
  • (b) Finite for all the materials material
  • (c) Zero-for some materials and non-zero for others
  • (d) Unpredictable for any material

Q7. Nernst heat theorem is another way of stating

  • (a) first law of thermodynamics
  • (c) third law of thermodynamics
  • (b) second law of thermodynamics
  • (d) fourth law of thermodynamics

Q8. Which of the following best describes the relation between isothermal compressibility (κT) and adiabatic compressibility (κs) is

  • (a) κT > κs
  • (b) κT ≥ κs
  • (c) κT < κs
  • (d) κT ≤ κs

Q9. A thermally insulated cubical box has two chambers of equal volume. Initially one mole of a mono atomic ideal gas is placed in one of the chambers while the other chamber is kept empty. The gas slowly leaks through a small hole and eventually occupies the whole box. The change in entropy of the gas is given by

  • (a) R/ln2
  • (b) R ln2
  • (c) zero
  • (d) 2R

Q10. The change in entropy (in SI units) in an adiabatic free expansion of one mole of an ideal gas, to double its initial volume is

  • (a) 5.762
  • (b) 0
  • (c) 8.314
  • (d) 1.38

Q11. Consider a gas contained in a box at pressure P and temperature T having entropy S. If the box is divided into two parts of volume V1 and V2 with corresponding entropies S1 and S2 , then S-(S1+S2) is

  • (a) > 0
  • (b) < 0
  • (c) = 0
  • (d) none of these

Q12. The Clausius mathematical statement of the second law of thermodynamics, for an irreversible process is

  • (a) ∮ δQ/T ≤ 0
  • (b) ∮ δQ/T > 0
  • (c) ∮ δQ/T < 0
  • (d) ∮ δQ/T = 0

Q13. For any process, the second law ofthermodynamics requires that the change ofentropy ofthe universe be

  • (a) positive only
  • (b) positive or zero zero only
  • (c) zero only
  • (d) negative or zero

Q14. A rigid and thermally isolated tank is divided into two compartments of equal volume V, separated by a thin membrane. One compartment contains one mole on an ideal gas A and the other compartment contains one mole of a different ideal gas B . The two gases are in thermal equilibrium at a temperature T. If the membrane ruptures, the two gases mix. Assume that tie gases are chemically inert. The change in the total entropy of the gases on mixing is

  • (a) 0
  • (b) R ln2
  • (c) 3/2 R ln2
  • (d) 2R ln2

Q15. Consider a system of N atoms of an ideal gas of type A at temperature T and volume V. It is kept in diffusive contact with another system of N atoms of another ideal gas of type B at the same temperature T and volume V. Once the combined system reaches equilibrium,

  • (a) the total entropy of the final system is the same as the sum of the entropy of the individual system always.
  • (b) the entropy of mixing is 2NkB ln2.
  • (c) the entropy of the final system is less than that of sum of the initial entropies of the two gases
  • (d) The entropy of mixing is non-zero when the atoms A and B are of the same type.

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Answer Key (if you find any answer wrong, feel free to Correct us)

01.(b)06.(c)11.(b)
02.(d)07.(c)12.(c)
03.(a)08.(a)13.(b)
04.(b)09.(b)14.(d)
05.(c)10.(a)15.(b)

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