Question 1

Find the change in entropy (in J/K)when 5.00 moles of an ideal monatomic gas are allowed to expand isobarically from an initial volume of 20 cm3 to a final volume of 100 cm3.

Accepted Answer

A) 167 
B) 100 
C) 67 
D) 52 
E) 152

Question 2

An 800-MW electric power plant has an efficiency of 30%.It loses its waste heat in large cooling towers.Approximately how much waste heat (in MJ)is discharged to the atmosphere per second?

Accepted Answer

A) 1 200 
B) 1 900 
C) 800 
D) 560 
E) 240

Question 3

If n moles of an ideal gas are compressed isothermally from an initial volume V1 to a final volume V2,the change in entropy is

Accepted Answer

A) nR ln (V2/V1) 
B) nRT ln (V2/V1) 
C) nkB ln (V2/V1) 
D)  $n C _ { v } \int d T / T$ 
E) n Cv/T

Question 4

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 $\degree$F (15 $\degree$C)and the temperature well below the surface is 41 $\degree$F (5 $\degree$C)?

Accepted Answer

A) 3.5% 
B) 67% 
C) 31% 
D) 17% 
E) 96%

Question 5

What is the probability of rolling either a 7 or 11 on a single roll of a pair of dice?

Accepted Answer

A) 1/6 
B) 2/9 
C) 3/8 
D) 1/3 
E) 1/2

Question 6

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

Accepted Answer

A) 1 000 J 
B) 1 500 J 
C) 2 000 J 
D) 500 J 
E) 3 000 J

Question 7

One end of a copper rod is in thermal contact with a hot reservoir at T = 500 K and the other end is in thermal contact with a cooler reservoir at T = 300 K.Find the entropy change of each reservoir,and the total entropy change,when 8 000 J of heat energy are conducted from one end of the rod to the other with no change in the temperature distribution in the rod.

Accepted Answer

The answer of One end of a copper rod is...

Question 8

The thermal efficiency of a heat engine is given by

Accepted Answer

A)  $e = \frac { W _ { a g } } { \left| Q _ { h } \right| }$ . 
B)  $e = \frac { \left| Q _ { h } \right| - \left| Q _ { c } \right| } { \left| Q _ { h } \right| }$ . 
C)  $e = 1 - \frac { T _ { h } } { T _ { c } }$ . 
D) all of the formulas above. 
E) only (a)or (b)above.

Question 9

Which answer below is not a statement of the second law of thermodynamics?

Accepted Answer

A) Real processes proceed in a preferred direction. 
B) Energy does not flow spontaneously by heat from a cold to a hot reservoir. 
C) The entropy of the universe increases in all natural processes. 
D) In theory,heat engines working in a cycle employ reversible processes. 
E) You cannot construct a heat engine,operating in a cycle that does nothing but take heat from a reservoir and perform an equal amount of work.

Question 10

By operating a reversible heat engine with an ideal gas as the working substance in a Carnot cycle and measuring the ratio Qc/Qh,we can calculate

Accepted Answer

A) n,the number of moles of the ideal gas. 
B) the ratio Vc/Vh of the volumes of the ideal gas. 
C) the ratio Pc/Ph of the pressures of the ideal gas. 
D) the ratio PcVc/PhVh of the products of volumes and pressures of the ideal gas. 
E) the value of Avogadro's number.

Question 11

The change in entropy of a mass m of a solid substance which has a latent heat of fusion L and melts at a temperature T is

Accepted Answer

A) LT/m 
B) mL ln(T) 
C) mLT 
D) mL/T 
E) L/mT

Exam 18: Heat Engines,entropy,and the Second Law of Thermodynamics

Find the change in entropy (in J/K) when 5.00 moles of an ideal monatomic gas are allowed to expand isobarically from an initial volume of 20 cm³ to a final volume of 100 cm³.

An 800-MW electric power plant has an efficiency of 30%.It loses its waste heat in large cooling towers.Approximately how much waste heat (in MJ) is discharged to the atmosphere per second?

If n moles of an ideal gas are compressed isothermally from an initial volume V₁ to a final volume V₂,the change in entropy is

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 $\degree$ F (15 $\degree$ C) and the temperature well below the surface is 41 $\degree$ F (5 $\degree$ C) ?

What is the probability of rolling either a 7 or 11 on a single roll of a pair of dice?

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

The thermal efficiency of a heat engine is given by

Which answer below is not a statement of the second law of thermodynamics?

By operating a reversible heat engine with an ideal gas as the working substance in a Carnot cycle and measuring the ratio Q_c/Q_h,we can calculate

The change in entropy of a mass m of a solid substance which has a latent heat of fusion L and melts at a temperature T is

Exam 18: Heat Engines,entropy,and the Second Law of Thermodynamics

Find the change in entropy (in J/K) when 5.00 moles of an ideal monatomic gas are allowed to expand isobarically from an initial volume of 20 cm3 to a final volume of 100 cm3.

An 800-MW electric power plant has an efficiency of 30%.It loses its waste heat in large cooling towers.Approximately how much waste heat (in MJ) is discharged to the atmosphere per second?

If n moles of an ideal gas are compressed isothermally from an initial volume V1 to a final volume V2,the change in entropy is

What is the probability of rolling either a 7 or 11 on a single roll of a pair of dice?

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

The thermal efficiency of a heat engine is given by

Which answer below is not a statement of the second law of thermodynamics?

By operating a reversible heat engine with an ideal gas as the working substance in a Carnot cycle and measuring the ratio Qc/Qh,we can calculate

The change in entropy of a mass m of a solid substance which has a latent heat of fusion L and melts at a temperature T is

Find the change in entropy (in J/K) when 5.00 moles of an ideal monatomic gas are allowed to expand isobarically from an initial volume of 20 cm³ to a final volume of 100 cm³.

If n moles of an ideal gas are compressed isothermally from an initial volume V₁ to a final volume V₂,the change in entropy is

By operating a reversible heat engine with an ideal gas as the working substance in a Carnot cycle and measuring the ratio Q_c/Q_h,we can calculate