Exam 20: The Second Law of Thermodynamics

One of the most efficient engines built so far has the following characteristics: combustion chamber temperature = 1900°C exhaust temperature = 430°C 7.0 × 10⁹ cal of fuel produces 1.4 × 10¹⁰ J of work in one hour,where (a)What is the actual efficiency of this engine? (b)What is the Carnot efficiency of the engine? (c)What is the power output of this engine?

An air conditioner with a coefficient of performance of 3.5 uses 30 kW of power.How much power is it discharging to the outdoors?

A heat engine performs the reversible cycle abca with 9.0 moles of an ideal gas,as shown in the figure.Path ca is an adiabatic process.The temperatures at points a and b are 300 K and 500 K,respectively.The volume at point c is 0.20 m³.The adiabatic constant of the gas is .The thermal efficiency of this engine is closest to

A Carnot engine operates between reservoirs at 550K and 300K,discarding of heat in each cycle. (a)What is the engine's efficiency? (b)How much heat is supplied to the engine by the hot reservoir in each cycle?

The temperature inside a Carnot refrigerator placed in a kitchen at 22.0°C is 2.0°C.The heat extracted from the refrigerator is 89 MJ/h.What power is needed to operate this refrigerator?

A 2.00 kg piece of lead at 40.0°C is placed in a very large quantity of water at 10.0°C,and thermal equilibrium is eventually reached.Calculate the entropy change of the lead that occurs during this process.The specific heat of lead is 130 J/(kg • K).

Is it possible to transfer heat from a cold reservoir to a hot reservoir?

A 2.00 kg piece of lead at 40.0°C is placed in a very large quantity of water at 10.0°C,and thermal equilibrium is eventually reached.Calculate the TOTAL change in entropy that occurs during this process.The specific heat of lead is 130 J/(kg • K).

A Carnot engine is operated as a heat pump to heat a room in the winter.The heat pump delivers heat to the room at the rate of per second and maintains the room at a temperature of when the outside temperature is The power requirement for the heat pump under these operating conditions is closest to

A Carnot refrigerator has a coefficient of performance of 2.5.The refrigerator consumes 50 W of power.How much heat is removed from the interior of the refrigerator in 1 hour?

As a result of any natural process,the total entropy of any system plus that of its environment

A 810-g quantity of ethanol,in the liquid state at its melting point of is frozen at atmospheric pressure.The heat of fusion of ethanol is 1.04 × 10⁵ J/kg,the molecular mass is 46.1 g/mol,and the ideal gas constant is .The change in the entropy of the ethanol as it freezes is closest to

The second law of thermodynamics leads us to conclude that

A 2.00-kg block of ice at 0.00°C is dropped into a very large lake at 25.0°C and completely melts.For water,the heat of fusion is 3.35 × 10⁵ J/kg,the heat of vaporization is ,and the specific heat is .The net change in entropy of the system consisting of the ice and the lake due to this melting process is closest to

An ideal reversible refrigerator keeps its inside compartment at 9.0°C.What is the high temperature,T_h,needed to give this refrigerator a coefficient of performance of 3.7?

A refrigerator removes heat from the freezing compartment at the rate of 20 kJ and ejects 24 kJ into a room per cycle.How much work is required in each cycle?

According to the second law of thermodynamics,the entropy of any system always increases.

A certain engine extracts 1300 J of heat from a hot temperature reservoir and discharges 700 J of heat to a cold temperature reservoir.What is the efficiency of this engine?

What is the maximum theoretical efficiency possible for a heat engine operating between a reservoir in which ice and water coexist,and a reservoir in which water and steam coexist? The pressure is constant at 1.0 atmosphere for both reservoirs.

Is it possible to transfer heat from a hot reservoir to a cold reservoir?