Question 1

A solid 20.0-g mass of aluminum is at its melting point.What is the change in entropy the mass in the process of melting?

Accepted Answer

A) 3.24 * 10-3 kJ/K 
B) 4.58 * 10-3 kJ/K 
C) 6.15 * 10-3 kJ/K 
D) 8.50 * 10-3 kJ/K 
E) 9.11 * 10-3 kJ/K 
A) 3.24 * 10-3 kJ/K 
B) 4.58 * 10-3 kJ/K 
C) 6.15 * 10-3 kJ/K 
D) 8.50 * 10-3 kJ/K 
E) 9.11 * 10-3 kJ/K

Question 2

A refrigerator with a coefficient of performance of 3.6 is used to cool 3 liters of mineral water from room temperature (20S1U1P1$\circ$S1S1P0C)to 3S1U1P1$\circ$S1S1P0C.If the refrigerator runs at 525 W,how long will it take the water to reach 3S1U1P1$\circ$S1S1P0C? Recall that the heat capacity of water is 4.19 kJ/(kg K)and the density is 1 g/cm3.Assume the other contents of the refrigerator are already at 3F1F1F1S1F1F1F10C.

Accepted Answer

A) 43 s 
B) 113 s 
C) 407 s 
D) 68 s 
E) 26 s 
A) 43 s 
B) 113 s 
C) 407 s 
D) 68 s 
E) 26 s

Question 3

What is the maximum possible efficiency for a heat engine moving heat from temperature of 670S1U1P1$\circ$S1S1P0C to a region of 25S1U1P1$\circ$S1S1P0C?

Accepted Answer

A) 3.7% 
B) 32% 
C) 55% 
D) 68% 
E) 96% 
A) 3.7% 
B) 32% 
C) 55% 
D) 68% 
E) 96%

Question 4

The change in entropy of a system depends only on the initial and final states.This means that

Accepted Answer

A) the change in entropy for any process can be calculated. 
B) any process is reversible. 
C) entropy always increases. 
D) All are correct. 
E) None are correct. 
A) the change in entropy for any process can be calculated. 
B) any process is reversible. 
C) entropy always increases. 
D) All are correct. 
E) None are correct.

Exam 20: The Second Law of Thermodynamics

A solid 20.0-g mass of aluminum is at its melting point.What is the change in entropy the mass in the process of melting?

What is the maximum possible efficiency for a heat engine moving heat from temperature of 670 ∘\circ∘ C to a region of 25 ∘\circ∘ C?

The change in entropy of a system depends only on the initial and final states.This means that

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What is the maximum possible efficiency for a heat engine moving heat from temperature of 670^$\circ$C to a region of 25^$\circ$C?