Exam 20: Entropy and the Second Law of Thermodynamics

An ideal gas, consisting of n moles, undergoes a reversible isothermal process during which the volume changes from V_i to V_f. The change in entropy of the thermal reservoir in contact with the gas is given by:

A heat engine operates between a high temperature reservoir at T_H and a low temperature reservoir at T_L. Its efficiency is given by 1 - T_L/T_H:

A Carnot engine operates between 200 $\degree$ C and 20 $\degree$ C. Its maximum possible efficiency is:

For one complete cycle of a reversible heat engine, which of the following quantities is NOT zero?

A heat engine that in each cycle does positive work and loses energy as heat, with no heat energy input, would violate:

The change in entropy is zero for:

A refrigerator absorbs energy of magnitude $\mid$ Q_C $\mid$ as heat from a low temperature reservoir and rejects energy of magnitude $\mid$ Q_H $\mid$ as heat to a high temperature reservoir. Work W is done on the working substance. The coefficient of performance is given by:

For all adiabatic processes:

Let k be the Boltzmann constant. If the thermodynamic state of gas at temperature T changes isothermally and reversibly to a state with three timesthe number of microstates as initially, the energy input to gas as heat is:

Which of the following is NOT a state variable?

A Carnot heat engine operates between a hot reservoir at absolute temperature T_H and a cold reservoir at absolute temperature T_C. Its efficiency is:

A heat engine in each cycle absorbs energy from a reservoir as heat and does an equivalent amount of work, with no other changes. This engine violates:

A Carnot cycle:

The difference in entropy $\Delta$ S = S_B - S_A for two states A and B of a system can computed as the integral $\int$ dQ/T provided:

A cyclical process that transfers energy as heat from a high temperature reservoir to a low temperature reservoir with no other change would violate:

Which of the following processes leads to a change in entropy of zero for the system undergoing the process?

A hot object and a cold object are placed in thermal contact and the combination is isolated. They transfer energy until they reach a common temperature. The change $\Delta$ S_h in the entropy of the hot object, the change $\Delta$ S_c in the entropy of the cold object, and the change $\Delta$ S_total in the entropy of the combination are:

A slow (quasi-static) process is NOT reversible if:

A Carnot cycle heat engine operates between 400 K and 500 K. Its efficiency is:

An ideal gas expands into a vacuum in a rigid vessel. As a result there is: