Exam 11: Using Energy

A Carnot engine extracts 508 J of heat from a high-temperature reservoir during each cycle,and rejects 303 J of heat to a low-temperature reservoir during the same cycle.What is the efficiency of the engine?

What is the average kinetic energy of an ideal gas at 842 K? (The value of Boltzmann's constant is 1.38 × 10-²³ J/K. )

A perfectly insulated system has work done by it at a rate of 13 W.At what rate is the internal energy of the system changing?

A Carnot-efficiency engine operating between a reservoir of liquid mercury at its melting point and a colder reservoir extracts 15.0 J of heat from the mercury and does 4.0 J of work during each cycle.What is the temperature of the colder reservoir? Mercury melts at 233 K.

A laboratory experiment is to be run at 42.0 K.Express this temperature in Celsius to the nearest degree.

A heat engine that is 40% efficient and has a heat input of 200 J per cycle at the hot reservoir will waste 80 J of heat each cycle.

If two different gases are at the same temperature,the average translational kinetic energy per molecule must be the same for both of them.

You have a flask of liquid nitrogen at a temperature of -243°C.You then heat the nitrogen until its temperature is doubled.What is the new temperature?

Which of the following is a FALSE statement?

Is liberating heat through combustion a reversible or an irreversible process?

Water turns to ice when it is placed in a freezer.During this process,the entropy of this water has decreased.

Is temperature a macroscopic or a microscopic concept?

Heat can be transformed into work with 100% efficiency,but work cannot be transformed into heat with 100% efficiency.

Does an increase in entropy increase or decrease the ability of a system to do work?

A Carnot engine operates between a high temperature reservoir at 435 K and a river with water at 280 K.If it absorbs 3700 J of heat each cycle,how much work per cycle does it perform?

A heat engine operates between T_c = 294 K and T_h = 450 K.What is the maximum possible efficiency?

A refrigerator increases the entropy of its hot reservoir at the same time as it decreases the entropy of its cold reservoir,but a heat engine does just the opposite.

A Carnot engine operating between heat reservoirs at 10°C and 40°C has an efficiency of 75%.

Which of the following relationships are true for all types of heat engines? (There may be more than one correct choice. )

A 20% efficient heat engine that must do 50 J of work each cycle requires a heat input of 250 J per cycle.