Exam 19: The Second Law of Thermodynamics

In a nuclear power plant, heat is taken from the reactor core at 300ºC, work is done to drive an electric generator, and heat is rejected to the environment at 40ºC. What is the maximum possible thermal efficiency of this system?

A Carnot heat engine absorbs heat Q from a hot reservoir at 127ºC and exhausts heat to a cold reservoir at 27ºC. How much heat is exhausted to the cold reservoir?

An engine operating in a cycle would violate the second law of thermodynamics if it

What is the maximum possible coefficient of performance of a heat pump that is capable of maintaining the interior of a house at +20ºC when the temperature outside is -40ºC?

You want to construct a perfect refrigerator from a perfect heat engine. What else do you need?

A steam engine with a boiler temperature of 227ºC and an exhaust temperature of 27ºC has a maximum efficiency of approximately

A heat engine exhausts heat Q to a cold reservoir. The amount of work done by the engine

A heat engine with an output of 300 W has an efficiency of 25% and works at 10 cycles/s. How much heat is absorbed (Q_h) and how much rejected (Q_c) in each cycle?

For which of the following is COP the abbreviation?

The schematic diagram above illustrates a Carnot engine. Which two paths of the cycle is work done by the gas?

An ideal heat pump is used to pump head from the outside air at -5ºC to the hot-air supply for the heating fan in a house, which is at 35ºC. How much work is required to pump 1)5 kJ of heat into the house?

A substance undergoes a series of reversible processes that bring it back to its initial state. In this cycle, heat Q_x is absorbed by the substance and heat Q_y is rejected. The net amount of work performed by the substance is

The maximum theoretical thermal efficiency of a steam engine that is supplied steam at a temperature of 600ºC and exhausts it at a temperature of 200ºC is

A refrigerator extracts heat Q from a cold reservoir. The heat exhausted to a hot reservoir

A refrigerator extracts 25 kJ from a cold reservoir and rejects 35 kJ to a hot reservoir. What is the coefficient of performance of this refrigerator?

A thermodynamic system is taken in equilibrium steps from State I to State II. The quantities by which the process can be characterized are 1 internal energy, 2 entropy, 3 temperature, 4 work, and 5 heat. Of these quantities, those that are independent of path are

A box contains 10 red and 10 white marbles. The box is then given a good shake. What is the probability that all the 10 red marbles will be at the bottom of the box?

An electric power plant generates 100 MW of power at an efficiency of 35%. At what rate must water be circulated pass the condenser if the change in water temperature is not to exceed 10ºC?

A quantity of heat is removed from a hot reservoir at absolute temperature T and then is added to a cold reservoir at absolute temperature T/2. The cold reservoir experiences an entropy increase S. What is the change in the entropy of the universe?

Two moles of a gas at T = 350 K expand quasistatically and isothermally from an initial volume of 20 L to a final volume of 60 L. The change in entropy of the gas during this expansion is (R = 8.314 J/mol·K)