Exam 20: Second Law of Thermodynamics

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

If the theoretical efficiency of a Carnot engine is to be 100%, the heat sink must be

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?

The second law of thermodynamics leads us to conclude that

The total entropy of any system plus that of its environment increases as a result of any natural process.

What is the change in entropy when 50 g of ice melt at 0°C?

When 0.50 kg of ice freezes, the change in entropy is

From the energy that is input into an engine on each cycle, 500 kJ of mechanical work are produced and 600 kJ of heat are exhausted into the environment. What is the efficiency of the engine?

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

A gas consisting of 20.0 moles of monatomic ideal gas has a change in entropy of 200 J/K when taken through a process that starts at with a volume of 6.00 m³ at 300 K and ends with a volume 2.00 m³. The molar specific heat of the gas is 3R/2 for constant volume processes. What is the final temperature of the gas?

A Carnot cycle operates with an efficiency 0.60 between a low temperature heat bath at 20.0°C and a high temperature heat bath. What is the temperature of the high temperature heat bath?

If a system undergoes a reversible process,

What is the coefficient of performance of an ideal Carnot heat pump used to heat a house whose inside temperature is 24°C when the outdoor temperature is -12°C?

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?

The change in entropy of 20.0 moles of ideal monatomic constant volume gas as it changes from an initial temperature 300 K to its final temperature is 200 J/K. What is the final temperature of the gas?

According to the second law of thermodynamics, for any process that may occur within an isolated system, which one of the choices applies?

What is the maximum theoretical efficiency possible for an engine operating between 100°C and 400°C?

A 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?

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. (a) What is the actual efficiency of this engine? (b) What is the Carnot efficiency of the engine? (c) What is the power output, in hp, of this engine?

Calculate the entropy change of the lead that occurs when 2.00 kg of lead at 40.0°C are placed in a very large quantity of water at 10.0°C. The specific heat of lead is 0.031 cal/(g∙K).