Quiz — The Second Law of Thermodynamics

Question 1

In this lesson, what does global reversibility of a process require?

Accepted Answer

That a return process can restore the system and all its surroundings without leaving any other change.

Question 2

A closed system releases 2 400 J to a thermal reservoir at 300 K. Its entropy change is ΔS = −6 J/K. What are its exchanged entropy S_e and produced entropy S_i?

Accepted Answer

S_e = −8 J/K and S_i = +2 J/K.

Question 3

Heat Q = 1 200 J passes directly from a thermal reservoir at 600 K to one at 300 K. What is the total entropy change of the two reservoirs?

Accepted Answer

+2 J/K.

Question 4

Why does an ordinary refrigerator not contradict Clausius's statement?

Accepted Answer

Because heat transfer from cold to hot is accompanied by work supplied from outside.

Question 5

An ideal gas of n moles undergoes Joule–Gay-Lussac expansion from volume v to volume V > v in a rigid, adiabatic vessel. Removing the partition does not change the surroundings. Which balance is correct?

Accepted Answer

Q = W = ΔU_gas = 0 and ΔS_tot = nR ln(V/v) > 0.

Question 6

A two-reservoir engine operates between 600 K and 300 K and receives Q_H = 1 000 J per cycle. What is the maximum work supplied |W|?

Accepted Answer

500 J.

Question 7

Two subsystems of fixed composition can exchange energy and volume independently within an isolated whole. What can be said about their equilibrium state?

Accepted Answer

T_1 = T_2 and P_1 = P_2.

Question 8

A cyclic machine receives signed heats Q_k from reservoirs at T_k > 0 and exchanges work with an ideal source. Which statement respects the Clausius inequality and the lesson's definitions?

Accepted Answer

Σ_k Q_k/T_k ≤ 0; equality characterizes global reversibility without proving local reversibility.

Question 9

How does the lesson construct entropy from the equality ∮ δQ_rev/T = 0 for locally reversible cycles?

Accepted Answer

It defines S(B) − S(A) as the integral of δQ_rev/T.

Question 10

Which statement correctly describes local reversibility?

Accepted Answer

It requires every step in a succession of equilibrium states to be reversible through an infinitesimal change in the constraints.

Question 11

An irreversible process connects two equilibrium states A and B, but its intermediate states are far from equilibrium. Which statement is correct?

Accepted Answer

The entropy change ΔS can be calculated along a locally reversible path from A to B, whereas S_e and S_i depend on the actual process.

Question 12

Precisely which operation does the Kelvin–Planck statement forbid?

Accepted Answer

Completing a cycle whose sole effect is to extract heat Q > 0 from a single reservoir and supply W = −Q to the surroundings.

Question 13

A quasi-static compression is necessarily locally reversible.

Accepted Answer

False

Question 14

Which sequence describes the Carnot engine cycle of an ideal gas, with all branches locally reversible?

Accepted Answer

Isothermal expansion at T_H, reversible adiabatic expansion, isothermal compression at T_C, then reversible adiabatic compression.

Question 15

The second law fixes the thermodynamically allowed direction of evolution, but by itself determines neither its duration nor transport coefficients.

Accepted Answer

True