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Chapter 8: Thermochemistry: Chemical Energy
Problem Solving Center
Self Quiz 2
Self Quiz 2
This activity contains 20 questions.
An illustration of a state function involves a round-trip air flight from New York City to Denver in which a stop is made at Detroit on the way out and another stop is made at Memphis on the way back. The quantity that is the state function is
the distance flown.
the change in altitude.
the number of passengers.
the ticket price.
the amount of fuel used during the round-trip.
For a chemical reaction carried out at ________________ the change in internal energy can be attributed to _______________________.
constant pressure; heat transfer
constant volume; work and heat transfer
constant volume; work
constant pressure; work
constant volume; heat transfer
In order to ensure that comparisons of changes in enthalpy for reactions can be made, measurements of changes in enthalpy must be made under the conditions of
273 K, 1 atm pressure, and 1M concentration.
298 K, 1 atm pressure, and 1 M concentration.
273 K, 1 atm pressure, 1M concentration, and specified physical states.
0°C, 1 atm pressure, 1M concentration, and specified physical states.
298 K, 1 atm pressure, 1 M concentration for ions, and specified physical states.
In which reaction is work gained by the system?
CaCO
3
(
s
) ---> CaO(
s
) + CO
2
(
g
)
C
6
H
12
O
6
(
s
) + 6O
2
(
g
) ---> 6CO
2
(
g
) + 6H
2
O(
g
C
2
H
2
(
g
) + 2H
2
(
g
) ---> C
2
H
6
(
g
)
NaCl(
s
) + AgNO
3
(
s
) ---> AgCl(
s
) + NaNO
3
(
s
)
H
2
(
g
) + Cl
2
(
g
) ---> 2HCl(
g
)
The change in enthalpy for the reaction 2Fe
2
O
3
(
s
) + 6CO(
g
) ---> 4Fe(
s
) + 6CO
2
(
g
), if given the following information: 2Fe
2
O
3
(
s
) ---> 4Fe(
s
) + 3O
2
(
g
), change in enthalpy = +1684 kJ; and 2CO
2
(
g
) ---> 2CO(
g
) + O
2
(
g
), change in enthalpy = +566 kJ), is
-4.7 kJ.
+3382 kJ.
+2250 kJ.
1118 kJ.
-14 kJ.
The change in enthalpy for the reaction 2C(
s
) + O
2
(
g
) ---> 2CO(
g
), if given the following information: 2CO(
g
) + O
2
(
g
) ---> 2CO
2
(
g
), change in enthalpy = -566 kJ; and, C(
s
) + O
2
(
g
) ---> CO
2
(
g
), change in enthalpy = -394 kJ is
-1354 kJ.
+172 kJ.
-222 kJ.
+1354 kJ.
-960 kJ.
The enthalpy change for the reaction 2C
2
H
6
+ 5O
2
(
g
) ---> 4CO(
g
) + 6H
2
O(
l
) is (Enthalpies of formation are -84.7 kJ/mole for C
2
H
6
, -110.5 kJ/mole for CO(
g
), -241.8 kJ/mole for H
2
O(
g
), and -285.8 kJ/mole for H
2
O(
l
).)
-311.6 kJ.
+1987.4 kJ.
-1723.4 kJ.
-1987.4 kJ.
+311.6 kJ.
The enthalpy change for the reaction N
2
(
g
) + 3Cl
2
(
g
) ---> 2NCl
3
(
g
) is (Bond dissociation energies are 240 kJ/mole for N-N, 418 kJ/mole for N
N, 945 kJ/mole for N
N, 243 kJ/mole Cl-Cl, and 200 kJ/mole for N-Cl.)
-231 kJ.
-53 kJ.
-474 kJ.
+1074 kJ.
+474 kJ.
What is the enthalpy of formation of K
2
O(
s
) if the enthalpy change for the reaction K
2
O(
s
) + H
2
O(
l
) ---> 2KOH(
s
) is -202.3 kJ? (Enthalpies of formation are -285.8 kJ/mole for H
2
O(
l
) and -424.8 kJ/mole for KOH.)
-341.3 kJ/mole.
-361.5 kJ/mole.
766.1 kJ/mole.
+63.3 kJ/mole.
-766.1 kJ/mole.
What is the specific heat of lithium if adding 304 J of energy causes the temperature of a 10.0-g sample to increase from 20.0°C to 28.5°C?
1.07
3.58
24.8
0.280
2.58 x 10
4
What is the value for the change in enthalpy (in kilojoules) for the reaction NO
2
(
g
) ---> 1/2N
2
(
g
) + O
2
(
g
), if the reaction N
2
(
g
) + 2O
2
(
g
) ---> 2NO
2
(
g
) has a change in enthalpy of +66 kJ?
+0.015
+0.030
+33
-66
-33
What is the value for the change in internal energy (in kilojoules) for the reaction 2O
3
(
g
) ---> 3O
2
(
g
), which has a change in enthalpy = -286.0 kJ, if the reaction is carried out at constant pressure of 1.0 atm and the volume of the reaction changes from 50.0 L to 75.0 L?
-286.0
+283.5
-311.0
-283.5
-288.5
When 50.0 mL of 1.00 M HCl is mixed with 50.0 mL of 1.00 M NaOH in a calorimeter, a neutralization reaction takes place in which the temperature of the mixture increases from 25.0°C to 31.6°C. If the density of the mixture is assumed to be 1.00 g/mL and its specific heat is assumed to be 4.18 J/g
.
°C, how much heat (in kJ) is released or absorbed by this reaction, assuming the calorimeter absorbs very little heat?
The correct answer is -13.2.
The correct answer is -2.76.
The correct answer is +2.76.
The correct answer is -23.6.
The correct answer is -1.38.
When a chemical reaction occurs in which the products are more stable than the reactants,
the potential energy of the products is greater than the potential energy of the reactants.
the potential energy of the reactants is completely transferred to the products.
some of the potential energy of the reactants is transformed into kinetic energy.
the total amount of kinetic and potential energy of the chemicals in the reaction increases.
the total amount of kinetic and potential energy of the chemicals in the reaction decreases.
Which process does
not
represent the conversion of potential energy to kinetic energy?
A flashlight turned on does
not
represent the conversion of potential energy to kinetic energy.
A mousetrap set to catch a mouse does
not
represent the conversion of potential energy to kinetic energy.
Coal undergoing combustion and providing heat does
not
represent the conversion of potential energy to kinetic energy.
A ball rolling down a ramp does
not
represent the conversion of potential energy to kinetic energy.
A balloon popped by a needle does
not
represent the conversion of potential energy to kinetic energy.
Which reaction will have a positive change in entropy?
CH
4
(
g
) + 4Cl
2
(
g
) ---> CCl
4
(
l
) + 4HCl(
g
)
Ag
+
(
aq
) + Cl
-
(
aq
) ---> AgCl(
s
)
C
3
H
8
(
g
) + 5O
2
(
g
) ---> 3CO
2
(
g
) + 4H
2
O(
g
)
2Hg(
l
) + O
2
(
g
) ---> 2HgO(
s
)
HCCH(
g
) + 2H
2
(
g
) ---> CH
3
CH
3
(
g
)
Which relationship between enthalpies of reaction, entropy changes, and spontaneity is correctly stated?
Processes with negative values of enthalpies of reaction and positive entropy changes are always spontaneous.
Processes with negative values of enthalpies of reaction and positive entropy changes are always nonspontaneous.
Processes with negative values of enthalpy and negative values of entropy are always nonspontaneous.
Processes with positive values of enthalpies of reaction and positive entropy changes are always nonspontaneous.
Processes with positive values of enthalpies of reaction and negative entropy changes can be spontaneous.
Which statement describes an exothermic process?
When 1 mole of liquid acetone vaporizes, it absorbs 33 kJ of heat.
When 1 mole of methane vaporizes, 0.94 kJ of heat are absorbed.
When 1 mole of Pb melts, 4.8 kJ of heat are absorbed by the lead.
When 1 mole of water melts, 6.0 kJ of heat are released by the surroundings.
When 1 mole of acetic acid condenses, the surroundings gain 23.4 kJ of heat.
Which statement does
not
describe an endothermic process?
When 1 mole of acetic acid freezes, the surroundings gain 8.8 kJ.
One mole of C
8
H
18
(
l
) has a change in enthalpy of +49.6 kJ when it vaporizes.
When 1 mole of acetic acid melts, the surroundings will lose 11.5 kJ of water.
When 1 mole of acetone vaporizes, 33 kJ of heat are absorbed by the acetone.
The process 2H
2
O(
g
) ---> 2H
2
(
g
) + O
2
(
g
) has a change in enthalpy = +484 kJ.
Which statement gives the correct relationship between the sign of the change in internal energy and the system?
The change in internal energy is positive if E
initial
is greater than E
final
.
The change in internal energy is positive if energy flows out of the system and into the surroundings.
The change in internal energy is negative if energy flows out of the surroundings and into the system.
The change in internal energy is positive if energy flows out of the surroundings and into the system.
The change in internal energy is negative if E
final
is greater than E
initial
.
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