exam 3 ch 17

Question 1

Which process is spontaneous?

movement of a ball from the bottom to the top of a slide
diffusion of gas from low pressure to high pressure
dissolution of sand in water
saltwater converting into salt crystals and water
evaporation of gasoline

Answer 1

evaporation of gasoline

Question 2

According to the second law of thermodynamics, the change in the entropy of the universe (ΔSuniv) during a spontaneous reaction is

zero.
negative.
positive.
less than the change in entropy of the system (ΔSsys).
greater than the change in entropy of the system (ΔSsys).

Answer 2

positive.

Question 3

Which process is nonspontaneous?

Iron in the open air rusts.
Liquid water in a freezer turns to ice.
A spark ignites a mixture of propane and air.
Perfume diffuses in a room.
Heat flows from a cold body to a hot body.

Answer 3

Heat flows from a cold body to a hot body.

Question 4

In a spontaneous process, which of the following always increases?

the entropy of the system
the entropy of the surroundings
the entropy of the universe
the entropy of the system and the universe
the entropy of the system, the surroundings, and the universe

Answer 4

the entropy of the universe

Question 5

During a spontaneous chemical reaction, it is found that ΔSsys< 0. This means

ΔSsurr< 0, and its magnitude is less than ΔSsys.
ΔSsurr< 0, and its magnitude is greater than ΔSsys.
ΔSsurr> 0, and its magnitude is less than ΔSsys.
ΔSsurr> 0, and its magnitude is greater than ΔSsys.
ΔSuniv< 0.

Answer 5

ΔSsurr> 0, and its magnitude is greater than ΔSsys.

Question 6

For a nonspontaneous chemical reaction, it is found that ΔSsys> 0. Which of the following could be true?

ΔSsurr< 0, and its magnitude is less than ΔSsys
ΔSsurr> 0, and its magnitude is less than ΔSsys
ΔSsurr< 0, and its magnitude is greater than ΔSsys
ΔSsurr> 0, and its magnitude is greater than ΔSsys
ΔSuniv> 0

Answer 6

ΔSsurr< 0, and its magnitude is greater than ΔSsys

Question 7

What is the entropy change to the surroundings when one mole of ice melts in someone’s hand if the hand temperature is 32°C? Assume a final temperature for the water of 0°C. The heat of fusion of ice is 6.01 kJ/mol.

-188 J/K
+19.7 J/K
-22.0 J/K
+188 J/K
-19.7 J/K

Answer 7

-19.7 J/K

Question 8

If one mole of ice melts at its melting point of 273 K, the entropy change for the ice is 22.0 J/K. If the ice melts in someone’s hand at 34°C, what is the change in the entropy of the universe? Assume a final temperature for the water of 0°C. The enthalpy of fusion for ice is 6.01 kJ/mol.

+19.6 J/K
-2.4 J/K
-19.6 J/K
+41.5 J/K
+2.4 J/K

Answer 8

+2.4 J/K

Question 9

The entropy change of the surroundings, ΔSsurr, is related to heat transfer, q, with respect to the system and temperature T by

-q/Tsys=ΔSsurr.
+q/Tsys=ΔSsurr.
-q/Tsurr=ΔSsurr.
q/Tsurr=ΔSsurr.
None of these are correct, unless the system undergoes a reversible process.

Answer 9

-q/Tsurr=ΔSsurr.

Question 10

Care must be taken when dissolving solid pellets of sodium hydroxide (NaOH) in water, because the temperature of the water can rise dramatically. Taking NaOH as the system, what can you deduce about the signs of the entropy change of the system (ΔSsys) and surroundings (ΔSsurr) from this?

ΔSsys< 0 and ΔSsurr< 0
ΔSsys< 0 and ΔSsurr> 0
ΔSsys> 0 and ΔSsurr< 0
ΔSsys> 0 and ΔSsurr> 0
Nothing can be deduced from this limited information.

Answer 10

ΔSsys> 0 and ΔSsurr> 0

Question 11

The enthalpy of fusion for carbon tetrachloride (CCl4) is 2.67 kJ/mol, and its melting point is 250 K. What is the entropy change when 2.0 mol of carbon tetrachloride melts at 250 K?

21.4 J/K
0.0214 J/K
10.7 J/K
0.0107 J/K
-668 J/K

Answer 11

21.4 J/K

Question 12

The enthalpy of fusion for benzene (C6H6) is 127.40 kJ/kg, and its melting point is 5.5°C. What is the entropy change when one mole of benzene melts at 5.5°C?

9.95 kJ/K
1.81 J/K
35.7 J/K
127.40 kJ/K
1809 J/K

Answer 12

35.7 J/K

Question 13

The enthalpy of vaporization for toluene (C7H8) is 380.00 kJ/kg, and its boiling point is 110.6°C. What is the entropy change when 0.75 mol of toluene vaporizes at 110.6°C?

743 J/K
36.3 J/K
139 J/K
253 kJ/K
68.5 J/K

Answer 13

68.5 J/K

Question 14

The gas above the liquid in a sealed bottle of soda is primarily carbon dioxide. Carbon dioxide is also dissolved in the soda. When the distribution of carbon dioxide between the gas and liquid is at equilibrium, molecules of carbon dioxide in the gas phase can still dissolve in the liquid phase if they strike the surface and are captured. Similarly, molecules of carbon dioxide can escape from the liquid phase. What is the entropy change of the universe, ΔSuniv, for the dissolution of carbon dioxide under these conditions?

ΔSuniv< 0, because the dissolved carbon dioxide has fewer accessible states.
ΔSuniv> 0, because the dissolved carbon dioxide has fewer accessible states.
ΔSuniv= 0, because this is an equilibrium situation.
ΔSuniv< 0, because the gas dissolves spontaneously.
ΔSuniv> 0, because the gas dissolves spontaneously.

Answer 14

ΔSuniv= 0, because this is an equilibrium situation.

Question 15

Which process will lead to a decrease in the entropy of the system?

Salt crystals dissolve in water.
Air escapes from a hole in a balloon.
Iron and oxygen react to form rust.
Ice melts in your hand.
None of these lead to a negative change in the entropy of the system, because they are all spontaneous.

Answer 15

Iron and oxygen react to form rust.

Question 16

At 0 K, the entropy of a perfect crystal is

> 0.
= 0.
< 0.
0, = 0, or < 0, depending on the chemical structure of the crystal.
0 or = 0, depending on the chemical structure of the crystal

Answer 16

= 0.

Question 17

Which of the following will have the greatest standard molar entropy (S°)?

NH3(g)
H2O(l)
He(g)
CaCO3(s)
C(s, graphite)

Answer 17

NH3(g)

Question 18

Which of the following has the largest standard molar entropy (S°)?

CH4(g)
Na(s)
CH3CH2OH(l)
NH3(l)
CO2(s)

Answer 18

CH4(g)

Question 19

Which of the following is in the correct order of standard state entropy?

diamond is less than graphite
CH3CH2CH3 is less than CH3CH3
liquid water is less than solid water
HBr(g) is less than HBr(aq)
NH3 is less than H2

Answer 19

diamond is less than graphite