entropy contributions by: john l. falconer will medlin department of chemical and biological...

EntropyContributions by:

John L. Falconer & Will MedlinDepartment of Chemical and Biological Engineering

University of ColoradoBoulder, CO 80309-0424

Supported by the National Science Foundation

You have 4 balls: red, green blue, and yellow. You distribute them all into two cans. How many different ways can you do this?

A. 4

B. 8

C. 12

D. 16

E. None of the above

A gas is compressed isothermally. The entropy of the surroundings ________.

A. increases

B. decreases

C. remains the same.

D. Insufficient information.

What external pressure should be used in the WEC term when calculating the entropy change for isothermal compression of an ideal gas?

A. A constant external pressure

B. An external pressure that is always equal to the system pressure

C. Either (A) or (B)

D. Neither (A) or (B)

Air flows steadily at constant pressure through a pipe that is heated by a furnace. As air flows through the pipe, the entropy of the air _______.

A. increases  

B. remains the same  

C. decreases  

D. Insufficient information

Si So

Which of the following systems will have the largest entropy change when the blue partition is removed? The ideal gases are initially at 1 atm.

N2 Vacuum

N2 N2

N2 O2

Vacuum O2

A

B

C

D

Which of the following systems will have the largest entropy change when the blue partition is removed? The gases are ideal.

2 atmN2

1 atmO2

3 atmN2

3 atmN2

2 atmN2

Vacuum

Vacuum1 atm

O2

A

B

C

D

When the blue partition is removed between the two ideal gases below, the change is entropy is DS = 3Rln(2). What is most correct expression for DG?

1 atm1 mol Ar

2 atm2 mol O2

A. ∆H-3RTln(2)

B. ∆H-3Rln(2)

C. -3RTln(2)

D. 3RTln(2)

E. ∆H+3RTln(2)

An ideal gas undergoes two irreversible processes between state 1 and state 2. For process A, 100 kJ of work was done by the gas. For process B, 200 kJ of work was done by the gas. Which process has the larger entropy change for the gas?

A. Process A

B. Process B

C. Both process have the same change in entropy of the gas

1 2100 kJ

1 2200 kJ

A gallon of hot water is mixed with a gallon of cold water in a perfectly insulated container. When the waters are mixed, the entropy _______.

A. increases

B. decreases 

C. remains the same

D. Insufficient information  

1.0 mol of hot water mixes adiabatically with 1.0 mol of cold water. The entropy change of the cold water is 0.21 J/(mol•K). The entropy change of the hot water is _______.

A. positive

B. < -0.21 J/(mol•K)

C. < 0.21 J/(mol•K)

D. > 0.21 J/(mol•K)

E. > -0.21 J/(mol•K)ΔS =

0.21 J/(mol•K)ΔS = ?

Consider a completely insulated system. A reaction takes place inside the system. Therefore the system’s entropy __________.

A. remains the same since Q = 0

B. increases

C. decreases

D. Need more information

System

Insulation Insulation

System

An endothermic reaction takes place in a completely insulated, closed container of fixed volume.What happens to the entropy of system?

A. Increases

B. Decreases

C. Does not change

System

Insulation Insulation

System

An exothermic reaction takes place in a completely insulated, closed container of fixed volume.What happens to the entropy of system?

A. Increases

B. Decreases

C. Does not change

System

Insulation Insulation

System

You raise the pressure of a gas at constant temperature in a closed, adiabatic system. The entropy of the gas ___________.

A. does not change since temperature is constant

B. does not change since there is no heat transfer

C. increases

D. decreases

This picture shows a DNA molecule on a surface with vertical pillars on half the surface. The DNA will _______.

A. move into the pillars more

B. move out onto the open area

C. stay where it is

Container A has 2 kg of water, and container B has 1 kg of water. Both containers are initially at 50oC. To each container, 20 kJ of heat is added. Which container has the greater total (NOT per kg water) entropy change?

A. AB. BC. Same entropy change for bothD. Need more information

1 kg water at 50oC 2 kg water at 50oC

A B

QA = 20 kJ QB = 20 kJ

In these piston-cylinder systems, when the red stop is removed, the ideal gas expands, and the piston moves until it hits the black stopper. Each system is adiabatic and starts at 10 atm and 25°C.Which has the largest entropy change?

A. A

B. B

C. C

D. All the same

18

2 kg

Vacuum

Gas

Piston

Block

A

1 kg

Vacuum

Gas

B

Vacuum

Gas

C

For which does entropy increase?

A. Constant V

B. Constant P

C. Both

D. Neither

Constant V

Constant P

Which system has the highest entropy if one mole of the same ideal gas is in each piston-cylinder?

A. A

B. B

C. Both have the same entropy

2 atm

50°C

10 atm50°C

A B

Which system has the greatest entropy change if 10 mol N2 are in each piston-cylinder, which are initially at 100°C. Both processes are reversible.A. A

B. B

C. Same change for both

AB

WA = 0 kJ WB = 50 kJ

QA=12 kJ QB=10 kJ

You lower the pressure of a gas at constant temperature in a closed, adiabatic system. The entropy of the gas ___________.

A. does not change since temperature is constant

B. does not change since there is no heat transfer

C. increases

D. decreases

Which is the best approximation to a constant pressure process for a gas on a H-S diagram?

H

S

A

H

SB

H

S

C

H

S

D

A B C

D E

Which is the correct plot of entropy of the system (S) vs. mole fraction of component i (yi) for a binary mixture of ideal gases?

yi

S

yi

S

yi

S

yi

S

yi

S

A gas goes from states A to B in a reversible adiabatic process. It then goes from B back to A by a different pathway that is irreversible and not adiabatic. The entropy change for the gas for the irreversible pathway is _______ zero.

A. greater than

B. less than

C. equal to

V

P

A

B

Rev.

Irrev.

Enthalpy

Pre

ssur

e

AB C

DE

Which line most likely corresponds to a constant entropy process?

One mol of CH4 at 1 bar and 50°C is mixed with 1 mol of O2 at 1 bar and 50°C. The final mixture is at 2 bar and 50°C. Assume ideal gases. The Gibbs free energy change is ___________.

A. positive

B. negative

C. zero

Which is the most correct plot of Gibbs free energyversus temperature for a single component?

T(K)T(K)A

Gib

bs (J

/g)

T-sat

0

BG

ibbs

(J/g

)T-sat

0

C

Gib

bs (J

/g)

T(K)T-sat

0

D

Gib

bs (J

/g)

T(K)T-sat

0

E

Gib

bs (J

/g)

T(K)T-sat

0

Which is the most correct plot of Gibb’s free energy versus pressure for a single component?

P(atm)P(atm)A

Gib

bs (J

/g)

P-sat

0

BG

ibbs

(J/g

)P-sat

0

C

Gib

bs (J

/g)

P(atm)P-sat

0

D

Gib

bs (J

/g)

P(atm)P-sat

0

E

Gib

bs (J

/g)

P(atm)P-sat

0

Two of these plots represent enthalpy and entropy vs. temperature for a pure component going from liquid to vapor. Identify the correct axes labels.

A. Y = S ; Z = H

B. W = S ; X = H

C. W = H ; X = S

D. Z = H ; X = S

E. R = H ;Z = S T(K)

Z

T(K)

X

T(K)

Y

T(K)

R

T(K)

W

For an ideal gas, if the pressure is increased while keeping the entropy constant, the enthalpy ________.

A. increases

B. decreases

C. remains the same

D. Need more information.

Two different paths can be used for a process that changes the state of a fluid from 300 K and 1 bar to 500 K and 9 bar. Path A is adiabatic and reversible, and Path B is non-adiabatic and irreversible. Which of the following statements is true?A. The change in entropy of the fluid will be greater for

path A

B. The change in entropy of the fluid will be greater for path B

C. Both paths will have the same change in entropy of the fluid, but the change will be positive

D. The compression in path A will require less work

Hydrogen storage often involves the sorption of hydrogen from the gas phase into a solid material, where it can be stored more densely. For the adsorption/desorption process involved in H2 storage, which process should be run at a lower temperature?

A. Adsorption of hydrogen into material.

B. Desorption of hydrogen from material.

C. It does not matter.

A functional protein is found in its native state (N) having a defined structure. A denatured protein (D) loses functionality because the structure is disturbedas bonds are broken. The enthalpy of a native protein is _________ the enthalpy of the denatured protein.

A. greater than

B. less than

C. the same as

denaturation

N D

A functional protein is found in its native state (N) having a defined structure. A denatured protein (D) loses functionality because the structure is disturbedas bonds are broken. The entropy of a native protein is _________ the enthalpy of the denatured protein.

A. greater than

B. less than

C. the same as

denaturation

N D

A functional protein is found in its native state (N) having a defined structure at 30°C. A denatured protein (D) loses functionality because the structure is disturbed and bonds are broken. This will occur spontaneously when temperature __________.

A. increases

B. decreases

C. remains the same

denaturation

N D