Question 1

Calculate the standard enthalpy change for the reaction 2C8H18(l)  + 21O2(g)  → 8CO(g)  + 8CO2(g)  + 18H2O(l) . Given:
2C8H18(l)  + 25O2(g)  → 16CO2(g)  + 18H2O(l)  ΔH° = -11,020. kJ/mol
2CO(g)  + O2(g)  → 2CO2(g)  ΔH° = -566.0 kJ/mol

Accepted Answer

A)   1.0454 × 104 kJ/mol
B)   -8756 kJ/mol
C)   1.1586 × 104 kJ/mol
D)   -6492 kJ/mol
E)   -1.0454 × 104 kJ/molF) C) and D)
G) A) and D)

Question 2

How much heat is released if 35.0 g of ethanol (C2H5OH)  burns in excess oxygen? C2H5OH(l)  + 3O2(g)  → 2CO2(g)  + 3H2O(l)  ΔH°rxn = -1367 kJ/mol

Accepted Answer

A)   1797 kJ
B)   1367 kJ
C)   9.61 × 10-4 kJ
D)   4.78 × 104 kJ
E)   1040 kJF) A) and E)
G) B) and C)

Question 3

Consider the following two representations of chemical reactions. Each sphere represents 1 mol of atoms. rxn for the following reaction? CS(g)  + O(g)  → CO(g)  + S(g)  A)  -359 kJ/mol B)  1434 kJ/mol C)  -7142 kJ/mol D)  -1434 kJ/mol E)  7142 kJ/mol" class="answers-bank-image d-inline" rel="preload" > What is ΔHºrxn for the following reaction? CS(g)  + O(g)  → CO(g)  + S(g)

Accepted Answer

A)   -359 kJ/mol
B)   1434 kJ/mol
C)   -7142 kJ/mol
D)   -1434 kJ/mol
E)   7142 kJ/molF) C) and D)
G) None of the above

Question 4

Octane (C8H18)  undergoes combustion according to the following thermochemical equation. 2C8H18(l)  + 25O2(g)  → 16CO2(g)  + 18H2O(l)  ΔH°rxn = -1.0940 × 104 kJ/mol
What is the standard enthalpy of formation of liquid octane?
ΔH°f(CO2(g) )  = -393.5 kJ/mol and ΔH°f(H2O(l) )  = -285.8 kJ/mol

Accepted Answer

A)   -250 kJ/mol
B)   -10,940. kJ/mol
C)   -2188 kJ/mol
D)   -495 kJ/mol
E)   495 kJ/molF) C) and D)
G) A) and D)

Question 5

For a particular process, 28 kJ of heat is absorbed and 15 kJ of work is done on the surroundings. What is ΔU?

Accepted Answer

A)   ΔU = +43 kJ
B)   ΔU = -43 kJ
C)   ΔU = -13 kJ
D)   ΔU = +13 kJ
E)   ΔU = +28 kJF) C) and D)
G) B) and C)

Question 6

________ is the amount of heat required to raise the temperature of one gram of a substance by one degree Celsius.

Accepted Answer

The answer of ________ is the amount of heat required...

Question 7

To which one of the following reactions, occurring at 25oC, does the symbol ΔHof [H2SO4(l) ] refer?

Accepted Answer

A)   H2(g)  + S(s)  + 2 O2(g)   H2SO4(l) 
B)   H2SO4(l)   H2(g)  + S(s)  + 2 O2(g) 
C)   H2(g)  + S(g)  + 2 O2(g)   H2SO4(l) 
D)   H2SO4(l)   2 H(g)  + S(s)  + 4 O(g) 
E)   2 H(g)  + S(g)  + 4 O(g)   H2SO4(l) F) A) and E)
G) B) and E)

Question 8

What is ΔH°rxn for the following reaction? 2C8H18(l)  + 17O2(g)  → 16CO(g)  + 18H2O(l) 
2C8H18(l)  + 25O2(g)  → 16CO2(g)  + 18H2O(l)  ΔH°rxn = -11020. kJ/mol
2CO(g)  + O2(g)  → 2CO2(g)  ΔH°rxn = -566.0 kJ/mol

Accepted Answer

A)   -11020. kJ/mol
B)   +6492 kJ/mol
C)   -1964 kJ/mol
D)   -6492 kJ/mol
E)   -11586 kJ/molF) D) and E)
G) C) and D)

Question 9

In which process is ΔH = ΔU?

Accepted Answer

A)   Two moles of ammonia gas are cooled from 325°C to 300°C at a constant pressure of 1.2 atm.
B)   One gram of water is vaporized at 100°C and 1 atm.
C)   Two moles of hydrogen iodide gas react to form hydrogen gas and iodine gas in a 40-L container.
D)   Solid calcium carbonate is heated to form solid calcium oxide and carbon dioxide gas in a container with variable volume.
E)   One mole of solid carbon dioxide sublimes to the gas phase.F) A) and B)
G) A) and C)

Question 10

What is ΔH°rxn for the decomposition of calcium carbonate to calcium oxide and carbon dioxide? CaCO3(s)  → CaO(s)  + CO2(g)  rxn for the decomposition of calcium carbonate to calcium oxide and carbon dioxide? CaCO3(s)  → CaO(s)  + CO2(g)    A)  -2236.0 kJ/mol B)  -1449.0 kJ/mol C)  -177.8 kJ/mol D)  177.8 kJ/mol E)  2236.0 kJ/mol" class="answers-bank-image d-inline" rel="preload" >

Accepted Answer

A)   -2236.0 kJ/mol
B)   -1449.0 kJ/mol
C)   -177.8 kJ/mol
D)   177.8 kJ/mol
E)   2236.0 kJ/molF) C) and E)
G) C) and D)

Question 11

Sand is converted to pure silicon in a three-step process. The final step in this process is as follows. SiCl4(g)  + 2Mg(s)  → 2MgCl(s)  + Si(s)  ΔH°rxn = -625.6 kJ/mol
What is the enthalpy change if 25.0 mol of silicon tetrachloride is converted to elemental silicon?

Accepted Answer

A)   -25.0 kJ
B)   -626 kJ
C)   -1.56 × l04 kJ
D)   -3.13 × 104 kJ
E)   -3.13 × 103 kJF) B) and E)
G) B) and C)

Question 12

Ethanol, C2H5OH, is promoted as a clean fuel and is used as an additive in many gasoline mixtures. Calculate the ΔH°rxn for the combustion of ethanol. 2H5OH, is promoted as a clean fuel and is used as an additive in many gasoline mixtures. Calculate the ΔH°rxn for the combustion of ethanol.   A)  -1235.4 kJ B)  -751.8 kJ C)  -358.3 kJ D)  358.3 kJ E)  1235.4 kJ" class="answers-bank-image d-inline" rel="preload" >

Accepted Answer

A)   -1235.4 kJ
B)   -751.8 kJ
C)   -358.3 kJ
D)   358.3 kJ
E)   1235.4 kJF) A) and C)
G) C) and E)

Question 13

What is ΔH°rxn for the following reaction? 2H2O2(l)  → 2H2O(l)  + O2(g) 
ΔH°f(H2O(l) )  = -285.8 kJ/mol, ΔH°f(H2O2(l) )  = -187.6 kJ/mol

Accepted Answer

A)   -196.4 kJ/mol
B)   98.2 kJ/mol
C)   -98.2 kJ/mol
D)   -473.4 kJ/mol
E)   -946.8 kJ/molF) None of the above
G) B) and D)

Question 14

For which reaction is ΔH approximately (or exactly)  equal to ΔU?

Accepted Answer

A)   H2(g)  + Br2(g)  → 2HBr(g) 
B)   H2O(l)  → H2O(g) 
C)   CaCO3(s)  → CaO(s)  + CO2(g) 
D)   2H(g)  + O(g)  → H2O(l) 
E)   CH4(g)  + 2O2(g)  → CO2(g)  + 2H2O(l) F) All of the above
G) B) and D)

Question 15

Chemical reactions in a bomb calorimeter occur at constant pressure.

Accepted Answer

A) True 
 B)False

Question 16

When 0.560 g of Na(s)  reacts with excess F2(g)  to form NaF(s) , 13.8 kJ of heat is evolved at standard-state conditions. What is the standard enthalpy of formation (ΔH°f)  of NaF(s) ?

Accepted Answer

A)   567 kJ/mol
B)   -24.8 kJ/mol
C)   -7.8 kJ/mol
D)   24.8 kJ/mol
E)   -567 kJ/molF) D) and E)
G) A) and B)

Question 17

Which of the following processes always results in an increase in the energy of a system?

Accepted Answer

A)   The system loses heat and does work on the surroundings.
B)   The system gains heat and does work on the surroundings.
C)   The system loses heat and has work done on it by the surroundings.
D)   The system gains heat and has work done on it by the surroundings.
E)   None of these is always true.F) B) and D)
G) All of the above

Question 18

Which represents the formation reaction for XeF4(g) ? Each sphere represents 1 mol of atoms.

Accepted Answer

A)   4(g) ? Each sphere represents 1 mol of atoms. 
A)     
B)     
C)     
D)     
E)    " class="answers-bank-image d-inline" rel="preload" >
B)   4(g) ? Each sphere represents 1 mol of atoms. 
A)     
B)     
C)     
D)     
E)    " class="answers-bank-image d-inline" rel="preload" >
C)   4(g) ? Each sphere represents 1 mol of atoms. 
A)     
B)     
C)     
D)     
E)    " class="answers-bank-image d-inline" rel="preload" >
D)   4(g) ? Each sphere represents 1 mol of atoms. 
A)     
B)     
C)     
D)     
E)    " class="answers-bank-image d-inline" rel="preload" >
E)   4(g) ? Each sphere represents 1 mol of atoms. 
A)     
B)     
C)     
D)     
E)    " class="answers-bank-image d-inline" rel="preload" >F) B) and D)
G) D) and E)

Question 19

Which relationship is always correct?

Accepted Answer

A)   potential energy + kinetic energy = constant
B)   Δ = q + w
C)   ΔU = ΔH - PΔV
D)   H = U + PV
E)   ΔH = qVF) A) and C)
G) A) and B)

Question 20

If 325 g of water at 4.2°C absorbs 12.28 kJ of heat, what is the final temperature of the water? The specific heat of water is 4.184 J/g·°C.

Accepted Answer

A)   4.21°C
B)   4.8°C
C)   9.0°C
D)   13.2°C
E)   2938°CF) A) and D)
G) None of the above

Exam 5: Thermochemistry

Which represents the formation reaction for XeF₄(g) ? Each sphere represents 1 mol of atoms.

Correct Answer
verified

Consider the following two representations of chemical reactions. Each sphere represents 1 mol of atoms. What is ΔHº_rxn for the following reaction? CS(g) + O(g) → CO(g) + S(g)

Correct Answer
verified

Ethanol, C₂H₅OH, is promoted as a clean fuel and is used as an additive in many gasoline mixtures. Calculate the ΔH°_rxn for the combustion of ethanol.

Correct Answer
verified

Sand is converted to pure silicon in a three-step process. The final step in this process is as follows. SiCl₄(g) + 2Mg(s) → 2MgCl(s) + Si(s) ΔH°_rxn = -625.6 kJ/mol What is the enthalpy change if 25.0 mol of silicon tetrachloride is converted to elemental silicon?

Correct Answer
verified

To which one of the following reactions, occurring at 25^oC, does the symbol ΔH^o_f [H₂SO₄(l) ] refer?

Correct Answer
verified

Calculate the standard enthalpy change for the reaction 2C₈H₁₈(l) + 21O₂(g) → 8CO(g) + 8CO₂(g) + 18H₂O(l) . Given: 2C₈H₁₈(l) + 25O₂(g) → 16CO₂(g) + 18H₂O(l) ΔH° = -11,020. kJ/mol 2CO(g) + O₂(g) → 2CO₂(g) ΔH° = -566.0 kJ/mol

Correct Answer
verified

How much heat is released if 35.0 g of ethanol (C₂H₅OH) burns in excess oxygen? C₂H₅OH(l) + 3O₂(g) → 2CO₂(g) + 3H₂O(l) ΔH°_rxn = -1367 kJ/mol

Correct Answer
verified

Chemical reactions in a bomb calorimeter occur at constant pressure.

Correct Answer
verified

Which relationship is always correct?

Correct Answer
verified

Which of the following processes always results in an increase in the energy of a system?

Correct Answer
verified

What is ΔH°_rxn for the following reaction? 2H₂O₂(l) → 2H₂O(l) + O₂(g) ΔH°_f(H₂O(l) ) = -285.8 kJ/mol, ΔH°_f(H₂O₂(l) ) = -187.6 kJ/mol

Correct Answer
verified

________ is the amount of heat required to raise the temperature of one gram of a substance by one degree Celsius.

Correct Answer
verified

In which process is ΔH = ΔU?

Correct Answer
verified

What is ΔH°_rxn for the following reaction? 2C₈H₁₈(l) + 17O₂(g) → 16CO(g) + 18H₂O(l) 2C₈H₁₈(l) + 25O₂(g) → 16CO₂(g) + 18H₂O(l) ΔH°_rxn = -11020. kJ/mol 2CO(g) + O₂(g) → 2CO₂(g) ΔH°_rxn = -566.0 kJ/mol

Correct Answer
verified

What is ΔH°_rxn for the decomposition of calcium carbonate to calcium oxide and carbon dioxide? CaCO₃(s) → CaO(s) + CO₂(g)

Correct Answer
verified

Correct Answer
verified

For a particular process, 28 kJ of heat is absorbed and 15 kJ of work is done on the surroundings. What is ΔU?

Correct Answer
verified

For which reaction is ΔH approximately (or exactly) equal to ΔU?

Correct Answer
verified

If 325 g of water at 4.2°C absorbs 12.28 kJ of heat, what is the final temperature of the water? The specific heat of water is 4.184 J/g·°C.

Correct Answer
verified

When 0.560 g of Na(s) reacts with excess F₂(g) to form NaF(s) , 13.8 kJ of heat is evolved at standard-state conditions. What is the standard enthalpy of formation (ΔH°_f) of NaF(s) ?

Correct Answer
verified

Exam 5: Thermochemistry

Which represents the formation reaction for XeF4(g) ? Each sphere represents 1 mol of atoms.

Correct AnswerverifiedShow Answer

Consider the following two representations of chemical reactions. Each sphere represents 1 mol of atoms. What is ΔHºrxn for the following reaction? CS(g) + O(g) → CO(g) + S(g)

Correct AnswerverifiedShow Answer

Ethanol, C2H5OH, is promoted as a clean fuel and is used as an additive in many gasoline mixtures. Calculate the ΔH°rxn for the combustion of ethanol.

Correct AnswerverifiedShow Answer

Sand is converted to pure silicon in a three-step process. The final step in this process is as follows. SiCl4(g) + 2Mg(s) → 2MgCl(s) + Si(s) ΔH°rxn = -625.6 kJ/mol What is the enthalpy change if 25.0 mol of silicon tetrachloride is converted to elemental silicon?

Correct AnswerverifiedShow Answer

To which one of the following reactions, occurring at 25oC, does the symbol ΔHof [H2SO4(l) ] refer?

Correct AnswerverifiedShow Answer

Calculate the standard enthalpy change for the reaction 2C8H18(l) + 21O2(g) → 8CO(g) + 8CO2(g) + 18H2O(l) . Given: 2C8H18(l) + 25O2(g) → 16CO2(g) + 18H2O(l) ΔH° = -11,020. kJ/mol 2CO(g) + O2(g) → 2CO2(g) ΔH° = -566.0 kJ/mol

Correct AnswerverifiedShow Answer

How much heat is released if 35.0 g of ethanol (C2H5OH) burns in excess oxygen? C2H5OH(l) + 3O2(g) → 2CO2(g) + 3H2O(l) ΔH°rxn = -1367 kJ/mol

Correct AnswerverifiedShow Answer

Chemical reactions in a bomb calorimeter occur at constant pressure.

Correct AnswerverifiedShow Answer

Which relationship is always correct?

Correct AnswerverifiedShow Answer

Which of the following processes always results in an increase in the energy of a system?

Correct AnswerverifiedShow Answer

What is ΔH°rxn for the following reaction? 2H2O2(l) → 2H2O(l) + O2(g) ΔH°f(H2O(l) ) = -285.8 kJ/mol, ΔH°f(H2O2(l) ) = -187.6 kJ/mol

Correct AnswerverifiedShow Answer

________ is the amount of heat required to raise the temperature of one gram of a substance by one degree Celsius.

Correct AnswerverifiedShow Answer

In which process is ΔH = ΔU?

Correct AnswerverifiedShow Answer

What is ΔH°rxn for the following reaction? 2C8H18(l) + 17O2(g) → 16CO(g) + 18H2O(l) 2C8H18(l) + 25O2(g) → 16CO2(g) + 18H2O(l) ΔH°rxn = -11020. kJ/mol 2CO(g) + O2(g) → 2CO2(g) ΔH°rxn = -566.0 kJ/mol

Correct AnswerverifiedShow Answer

What is ΔH°rxn for the decomposition of calcium carbonate to calcium oxide and carbon dioxide? CaCO3(s) → CaO(s) + CO2(g)

Correct AnswerverifiedShow Answer

Octane (C8H18) undergoes combustion according to the following thermochemical equation. 2C8H18(l) + 25O2(g) → 16CO2(g) + 18H2O(l) ΔH°rxn = -1.0940 × 104 kJ/mol What is the standard enthalpy of formation of liquid octane? ΔH°f(CO2(g) ) = -393.5 kJ/mol and ΔH°f(H2O(l) ) = -285.8 kJ/mol

Correct AnswerverifiedShow Answer

For a particular process, 28 kJ of heat is absorbed and 15 kJ of work is done on the surroundings. What is ΔU?

Correct AnswerverifiedShow Answer

For which reaction is ΔH approximately (or exactly) equal to ΔU?

Correct AnswerverifiedShow Answer

If 325 g of water at 4.2°C absorbs 12.28 kJ of heat, what is the final temperature of the water? The specific heat of water is 4.184 J/g·°C.

Correct AnswerverifiedShow Answer

When 0.560 g of Na(s) reacts with excess F2(g) to form NaF(s) , 13.8 kJ of heat is evolved at standard-state conditions. What is the standard enthalpy of formation (ΔH°f) of NaF(s) ?

Correct AnswerverifiedShow Answer

Which represents the formation reaction for XeF₄(g) ? Each sphere represents 1 mol of atoms.

Correct Answer
verified

Consider the following two representations of chemical reactions. Each sphere represents 1 mol of atoms. What is ΔHº_rxn for the following reaction? CS(g) + O(g) → CO(g) + S(g)

Correct Answer
verified

Ethanol, C₂H₅OH, is promoted as a clean fuel and is used as an additive in many gasoline mixtures. Calculate the ΔH°_rxn for the combustion of ethanol.

Correct Answer
verified

Sand is converted to pure silicon in a three-step process. The final step in this process is as follows. SiCl₄(g) + 2Mg(s) → 2MgCl(s) + Si(s) ΔH°_rxn = -625.6 kJ/mol What is the enthalpy change if 25.0 mol of silicon tetrachloride is converted to elemental silicon?

Correct Answer
verified

To which one of the following reactions, occurring at 25^oC, does the symbol ΔH^o_f [H₂SO₄(l) ] refer?

Correct Answer
verified

Calculate the standard enthalpy change for the reaction 2C₈H₁₈(l) + 21O₂(g) → 8CO(g) + 8CO₂(g) + 18H₂O(l) . Given: 2C₈H₁₈(l) + 25O₂(g) → 16CO₂(g) + 18H₂O(l) ΔH° = -11,020. kJ/mol 2CO(g) + O₂(g) → 2CO₂(g) ΔH° = -566.0 kJ/mol

Correct Answer
verified

How much heat is released if 35.0 g of ethanol (C₂H₅OH) burns in excess oxygen? C₂H₅OH(l) + 3O₂(g) → 2CO₂(g) + 3H₂O(l) ΔH°_rxn = -1367 kJ/mol

Correct Answer
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Correct Answer
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Correct Answer
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Correct Answer
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What is ΔH°_rxn for the following reaction? 2H₂O₂(l) → 2H₂O(l) + O₂(g) ΔH°_f(H₂O(l) ) = -285.8 kJ/mol, ΔH°_f(H₂O₂(l) ) = -187.6 kJ/mol

Correct Answer
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Correct Answer
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Correct Answer
verified

What is ΔH°_rxn for the following reaction? 2C₈H₁₈(l) + 17O₂(g) → 16CO(g) + 18H₂O(l) 2C₈H₁₈(l) + 25O₂(g) → 16CO₂(g) + 18H₂O(l) ΔH°_rxn = -11020. kJ/mol 2CO(g) + O₂(g) → 2CO₂(g) ΔH°_rxn = -566.0 kJ/mol

Correct Answer
verified

What is ΔH°_rxn for the decomposition of calcium carbonate to calcium oxide and carbon dioxide? CaCO₃(s) → CaO(s) + CO₂(g)

Correct Answer
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Correct Answer
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Correct Answer
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Correct Answer
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Correct Answer
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When 0.560 g of Na(s) reacts with excess F₂(g) to form NaF(s) , 13.8 kJ of heat is evolved at standard-state conditions. What is the standard enthalpy of formation (ΔH°_f) of NaF(s) ?

Correct Answer
verified