Exam 20: The Second Law of Thermodynamics

A system consists of two very large thermal reservoirs in contact with each other,one at temperature 300°C and the other at temperature 200°C.When 600 J of heat transfers from the 300°C reservoir to the 200°C reservoir,what is the change in entropy of this system?

A refrigerator has a coefficient of performance equal to 4.2.How much work must be done on the refrigerator in order to remove 250 J of heat from the interior?

The entropy of an isolated system must be conserved,so it never changes.

An engine manufacturer makes the claim that the engine they have developed will,on each cycle,take 100 J of heat out of boiling water at 100°C,do mechanical work of 80 J,and exhaust 20 J of heat at 10°C.What,if anything,is wrong with this claim?

A perfect Carnot engine operates between the temperatures of 300K and 700K,drawing 60 kJ of heat from the 700K reservoir in each cycle.How much heat is dumped into the 300K reservoir in each cycle?

A Carnot engine operates between a high temperature reservoir at and a river with water at If it absorbs of heat each cycle,how much work per cycle does it perform?

The graph in the figure shows a cycle for a heat engine for which = 35 J.What is the thermal efficiency of this engine?

An ideal Carnot engine operates between reservoirs having temperatures of 125°C and -20°C.Each cycle the heat expelled by this engine is used to melt 30.0 g of ice at 0.00°C.The heat of fusion of water is and the heat of vaporization of water is . (a)How much work does this engine do each cycle? (b)How much heat per cycle does this engine absorb at the hot reservoir?

A nuclear fission power plant has an actual efficiency of 39%.If of power are produced by the nuclear fission,how much electric power does the power plant output?

What is the change in entropy of 10.0 moles of ideal monatomic gas that reversibly undergoes the isothermal expansion shown in the figure? The ideal gas constant is .