Exam 22: Heat Engines, entropy, and the Second Law of Thermodynamics

When water of mass m and specific heat c is heated from absolute temperature T₁ to absolute temperature T₂,its change in entropy is

A vessel containing 5.0 kg of water at 10°C is put into a refrigerator.The 1/7 HP motor (1 HP = 746 W)runs for 5.0 minutes to cool the liquid to the refrigerator's low temperature,0°C.What is the κ of the refrigerator?

Every second at Niagara Falls,some 5000 m³ of water falls a distance of 50 m.What is the increase in entropy per second due to the falling water? (Assume a 20°C environment).

A heat engine absorbs 2 500 J of heat from a hot reservoir and expels 1 000 J to a cold reservoir.When it is run in reverse,with the same reservoirs,the engine pumps 2 500 J of heat to the hot reservoir,requiring 1 500 J of work to do so.Find the ratio of the work done by the heat engine to the work done by the pump.Is the heat engine reversible?

Ten kilograms of water at 0°C is mixed with 10 kg of water at 100°C.The change in entropy (in cal/K)of the system is

Selena states that Proves that entropy has a definite value at the beginning and end of an adiabatic free expansion.Ron says ,where W is the number of microstates of a given macrostate.Which one,if either,is correct?

Determine the change in entropy (in J/K)when 5.00 moles of an ideal gas at 0°C are compressed isothermally from an initial volume of 100 cm³ to a final volume of 20 cm³.

An ideal gas is allowed to expand adiabatically.Assume the process is reversible.The change in entropy is

A lawn mower has a 6-horsepower engine (1 HP = 750 W).If the engine has an efficiency of 20%,and the throttle is such that the engine cycles 10 times a second,the heat that is expelled in one cycle is

For a gas of N identical molecules of molecular volume V_m in total volume V at temperature T,the number of ways of locating the N molecules in the volume is

The thermal efficiency of a heat engine is given by

A Carnot cycle,operating as a heat engine,consists,in the order given,of

An engine is designed to obtain energy from the temperature gradient of the ocean.What is the thermodynamic efficiency of such an engine if the temperature of the surface of the water is 59°F (15°C)and the temperature well below the surface is 41°F (5°C)?

Find the change in entropy (in J/K)when 5.00 moles of an ideal gas undergo a free expansion from an initial volume of 20 cm³ to a final volume of 100 cm³.

The change in entropy of 1.00 kg of water that is heated from 50°C to 100°C is (in cal/K)

The reason that we can calculate the change in entropy of a system is that

A gasoline engine absorbs 2 500 J of heat and performs 1 000 J of mechanical work in each cycle.The amount of heat expelled in each cycle is

On a cold day,a heat pump absorbs heat from the outside air at 14°F (−10°C)and transfers it into a home at a temperature of 86°F (30°C).Determine the maximum κ of the heat pump.

A new electric power plant has an efficiency of 42%.For every 100 barrels of oil needed to run the turbine,how many are essentially lost as waste heat (in barrels of oil)to the environment?

An adiabatic free expansion of a gas in a thermally isolated container is not reversible because