Exam 20: Entropy and the Second Law of Thermodynamics

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 heat engine:

A heat engine operates between 200 K and 100 K.In each cycle it takes 100 J from the hot reservoir, loses 25 J to the cold reservoir, and does 75 J of work.This heat engine violates:

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

A Carnot engine operates with a cold reservoir at a temperature of T_L = 400 K and a hot reservoir at a temperature of T_H = 500 K.What is the net entropy change as it goes through a complete cycle?

A heat engine in each cycle absorbs energy of magnitude as heat from a high temperature reservoir, does work of magnitude , and then absorbs energy of magnitude as heat from a low temperature reservoir.If this engine violates:

A certain heat engine draws 500 cal/s from a water bath at 27°C and transfers 400 cal/s to a reservoir at a lower temperature.The efficiency of this engine 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:

The maximum theoretical efficiency of a Carnot engine operating between reservoirs at the steam point and at room temperature is about:

An inventor claims to have a heat engine that has efficiency of 40% when it operates between a high temperature reservoir of 150°C and a low temperature reservoir of 30°C.This engine:

One mole of an ideal gas expands reversibly and isothermally at temperature T until its volume is doubled.The change of entropy of this gas for this process is:

A force of 5 N stretches an elastic band at room temperature.The rate at which its entropy changes as it stretches is about:

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

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

An inventor suggests that a house might be heated by using a refrigerator to draw energy as heat from the ground and reject energy as heat into the house.He claims that the energy supplied to the house can exceed the work required to run the refrigerator.This:

A Carnot refrigerator runs between a cold reservoir at temperature T_L and a hot reservoir at temperature T_H.You want to increase its coefficient of performance.Of the following, which change results in the greatest increase in the coefficient? The value of $\Delta$ T is the same for all changes.

An ideal gas is to taken reversibly from state i, at temperature T₁, to other states labeled I, II, III, IV and V on the p-V diagram below.All are at the same temperature T_2. Rank the five processes according to the change in entropy of the gas, least to greatest.

According to the second law of thermodynamics:

For all irreversible processes involving a system and its environment:

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