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CHM2046-HW-Ch12 Thermodynamics
- At what pressure is the standard Gibbs free energy of formations reported?
A) 2 atm B) 1 atm C) 3 atm
- What is the △G° at 298 K if △H° is +72.7 kJ and △S° is + 112 J/K?
A) - 39.3 kJ B) +70.0 kJ C) +39.3 kJ
Estimate △G° rxn for the following reaction at 307 K.
CH
( g ) + 2 O
( g ) - > CO
(g) + H
O ( l
) △H°= -890.4 kJ; △ S°= -242.2 J /K
A)
+816.0 kJ
B)
+66.3 kJ
C)
-66.3 kJ
D)
-816.0 kJ
E)
-250 kJ
- What is the △S° if the △H° is +88.00 kJ and △G ° is +11.21 kJ?
A) + 258 J B) - 258 J C) +0.258 J
- Determine the standard free energy of formation,
△G°
f for phosphoric acid given the following:
A) - 1124.3 kJ/mol B) - 2697.0 kJ/mol C) - 4497.2 kJ/mol
- Arrange the following sets of systems in order of increasing entropy. Assume one mole of each substance and the temperature
for each.
H
2 ( g ), HBrO 4 ( g ), HBr( g )
A) HBr ( g ) < HBrO 4 ( g ) < H 2 ( g ) B) H 2 ( g ) < HBrO 4 ( g ) < HBr( g ) C) H 2 ( g ) < HBr ( g ) < HBrO 4 ( g )
- Arrange the following sets of systems in order of increasing entropy. Assume one mole of each substance and the temperature
for each.
H 2 O( l ), H 2 O( g ), H 2 O( s )
A) H 2 O( s ) < H 2 O( l ) < H 2 O( g ) B) H 2 O( l ) < H 2 O( g ) < H 2 O( s ) C) H 2 O( s ) < H 2 O( g ) < H 2 O( l )
- Predict the sign of the entropy change for the following processes.
(a) An ice cube is warmed to near its melting point.
(b) Exhaled breath forms fog on a cold morning.
(c) Snow melts.
A) (a) +, (b)-, (c) - B) (a) - , (b)-, (c) + C) (a) +, (b)-, (c) +
- What happens to the freezing point of water when ethylene glycol is added?
A) (a) +, (b)-, (c) + B) (a) - , (b)-, (c) + C) (a) +, (b)-, (c) -
- What is the difference between △ S and △ S ° for a chemical change?
A) △ S : any change in entropy under any set of conditions. △S°: any change in entropy at standard conditions (1 atm for
gases, 1 M for solutions); if no temperature information is provided, assume the temperature is
298.15 K
B) △ S : any change in entropy under any set of conditions. △ S °: any change in entropy at standard conditions (2 atm for
gases, 0.5 M for solutions); if no temperature information is provided, assume the temperature is 298.15 K
C) △ S : any change in entropy under any set of conditions. △ S °: any change in entropy at standard conditions (1 atm for
gases, 1 m for solutions); if no temperature information is provided, assume the temperature is
298.15 K
- Calculate
△S°
for the following change:
A) 50 J/K B) 107 J/K C) - 107 J/K
- Calculate
△S°
for the following change: 2H2(g) + O2(g) → 2H2O(l)
A) 326.6 J/K B) 520 J/K C) - 326.6 J/K
- A reactions has △H
°
298
= 100 kJ/mol and △S
°
298
= 250 J/mol
. K. Is the reaction spontaneous at room temperature? If not,
under what temperature conditions will it become spontaneous?
A) The reaction is not spontaneous at room temperature. It will become spontaneous when the the temperature
increased to 300 K or beyond
B) The reaction is not spontaneous at room temperature. It will become spontaneous when the the temperature
increased higher than 400 K or beyond
C) The reaction is spontaneous at room temperature. It will become non-spontaneous when the the temperature
increased to 400 K or beyond.
- A reactions has △H
°
298
= - 50 kJ/mol and △S
°
298
= - 250 J/mol.K. Is the reaction spontaneous at room temperature? If not,
under what temperature conditions will it become spontaneous? If spontaneous, under what temperature conditions will it
become non-spontaneous?
A) The reaction is non-spontaneous at room temperature. It will become spontaneous when the temperature decreased
until lower than 200K
B) The reaction is not spontaneous at room temperature. It will become spontaneous when the temperature increased
until higher than 400K
C) The reaction is spontaneous at room temperature. It will become non-spontaneous when the temperature increased
until higher than 200K
- Use the standard free energy data to determine the free energy change for each of the following reactions, which is run
under standard state conditions and 25 °C. Identify each as either spontaneous or non-spontaneous at these conditions.
A) 394.36 kJ/mol, non-spontaneous
B) - 394.36 kJ/mol, spontaneous
C) - 215.36 kJ/mol, spontaneous
- Use the standard free energy data to determine the free energy change for each of the following reactions, which is run
under standard state conditions and 25 °C. Identify each as either spontaneous or non-spontaneous at these conditions.
A) 29.4 kJ/mol, non-spontaneous
B) - 29.4 kJ/mol, spontaneous
C) - 235.36 kJ/mol, spontaneous
- One of the important reactions in the biochemical pathway glycolysis is the reaction of glucose- 6 - phosphate (G6P) to form
fructose- 6 - phosphate (F6P) as following, Is the reaction spontaneous or non-spontaneous under standard thermodynamic
conditions?
A) spontaneous B) at equilibrium C) non-spontaneous
- One of the important reactions in the biochemical pathway glycolysis is the reaction of glucose- 6 - phosphate (G6P) to form
fructose- 6 - phosphate (F6P) as following, Is the reverse reaction spontaneous or non-spontaneous under standard
thermodynamic conditions?
A) non-spontaneous B) at equilibrium C) spontaneous
- When ammonium chloride is added to water and stirred, it dissolves spontaneously and the resulting solution feels cold.
Without doing any calculations, deduce the signs of △ G , △ H , and △ S for this process.
A) △ G positive, △ H negative, and △ S negative
B) △ G negative, △ H positive, and △ S positive
C) △ G negative, △ H negative, and △ S positive
- Explain what happens as a reaction starts with △ G < 0 (negative) and reaches the point where △ G = 0.
A) The reaction is always at equilibrium from the beginning
B) The reverse reaction proceeds until equilibrium is reached
C) The forward reaction proceeds until equilibrium is reached
- In glycolysis, the reaction of glucose (Glu) to form glucose- 6 - phosphate (G6P) requires ATP to be present as described by
the following equation:
A) - 47 kJ B) 13kJ C) - 13kJ
