Question 1

A system initially has an internal energy U of 504 J.It undergoes a process during which it releases 111 J of heat energy to the surroundings,and does work of 222 J.What is the final energy of the system,in J?

Accepted Answer

A)  171 J
B)  393 J
C)  504 J
D)  615 J
E)  837 JF) D) and E)
G) B) and C)

Question 2

Cold packs,whose temperatures are lowered when ammonium nitrate dissolves in water,are carried by athletic trainers when transporting ice is not possible.Which of the following is true of this reaction?

Accepted Answer

A)  ΔH
B)  ΔH> 0,process is exothermic
C)  ΔH
D)  ΔH> 0,process is endothermic
E)  ΔH = 0,since cold packs are sealedF) B) and C)
G) B) and E)

Question 3

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) A) and B)
G) C) and D)

Question 4

If,as a pioneer,you wished to warm your room by taking an object heated on top of a pot-bellied stove to it,which of the following 15-pound objects,each heated to 100°C,would be the best choice? The specific heat capacity (in J/g·°C) for each substance is given in parentheses.Iron (0.450) ,copper (0.387) ,granite (0.79) ,gold (0.129) ,water (4.184) .

Accepted Answer

A)  iron
B)  copper
C)  granite
D)  gold
E)  H2OF) A) and D)
G) A) and E)

Question 5

What is ΔH°rxn for the following reaction? C6H6(l) + 15/2 O2(g) → 6CO2(g) + 3H2O(l) 
6C(graphite) + 3H2(g) → C6H6(l) 
ΔH°rxn = +49.0 kJ/mol
C(graphite) + O2(g) → CO2(g) 
ΔH°rxn = -393.5 kJ/mol
H2(g) + ½O2(g) → H2O(l) 
ΔH°rxn = -285.8 kJ/mol

Accepted Answer

A)  -630.3 kJ/mol
B)  -2597.8 kJ/mol
C)  -3169.4kJ/mol
D)  -3267.4 kJ/mol
E)  630.3 kJ/molF) C) and E)
G) All of the above

Question 6

Ethylene glycol,used as a coolant in automotive engines,has a specific heat capacity of 2.42 J/g°C.Calculate q when 3.65 kg of ethylene glycol is cooled from 132°C to 85°C.

Accepted Answer

A)  -1900 kJ
B)  -420 kJ
C)  -99 kJ
D)  -0.42 kJ
E)  -4.2 × 10-6 kJF) All of the above
G) B) and C)

Question 7

An exothermic reaction causes the surroundings to

Accepted Answer

A)  warm up.
B)  become acidic.
C)  expand.
D)  decrease its temperature.
E)  release CO2.F) A) and D)
G) B) and E)

Question 8

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 = q VF) B) and E)
G) A) and B)

Question 9

In an endothermic reaction,in going from the reactants to the products at the same temperature,the value of q is negative.

Accepted Answer

A) True 
 B)False

Question 10

Using Hess's law,what is ΔH°rxn for the following reaction? WO3(s) + 3H2(g) → W(s) + 3H2O(g) 
2W(s) + 3O2(g) →2WO3(s) ΔH°rxn = -1685.8 kJ/mol
2H2(g) + O2(g) → 2H2O(g) ΔH°rxn = -483.6 kJ/mol

Accepted Answer

A)  117.5 kJ/mol
B)  235.0 kJ/mol
C)  359.3 kJ/mol
D)  1202.2 kJ/mol
E)  2169.4 kJ/molF) A) and E)
G) A) and D)

Question 11

What is ΔH°rxn for the reaction 2Al2O3(s) → 4Al(s) + 3O2(g) ? ΔH°f(Al2O3(s) ) = -1670 kJ/mol

Accepted Answer

A)  3340 kJ/mol
B)  1670 kJ/mol
C)  -3340 kJ/mol
D)  -1670 kJ/mol
E)  -835 kJ/molF) A) and B)
G) B) and E)

Question 12

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 D)

Question 13

The sign of q when heat is absorbed by the system is ___________.

Accepted Answer

The answer of The sign of q when heat is...

Question 14

Solid sodium peroxide (Na2O2) reacts with liquid water yielding aqueous sodium hydroxide and oxygen gas.How much heat is released if 327.2 g of oxygen gas is produced from the reaction of sodium peroxide and water under standard-state conditions? Substance ΔH°f(kJ/mol) 
Na2O2 (s) -510.9
NaOH(aq) -469.6
H2O(l) -285.8

Accepted Answer

A)  46,630 kJ
B)  1457 kJ
C)  6689 kJ
D)  3345 kJ
E)  2914 kJF) A) and B)
G) B) and E)

Question 15

A system that does no work but which receives heat from the surroundings has

Accepted Answer

A)  q  0.
B)  q > 0,ΔU 
C)  q = ΔU.
D)  q = -ΔU.
E)  w = ΔU.F) D) and E)
G) B) and E)

Question 16

The work done on the surroundings by the expansion of a gas is w = -PΔV.

Accepted Answer

A) True 
 B)False

Question 17

Which equation has a ΔHrxn that is not equal to ΔHof of the product? rev: 04_28_2015_QC_CS-14747

Accepted Answer

A)  F2(g) + ½O2(g) → F2O(g) 
B)  O2(g) + 2H2(g) → 2 H2O(g) 
C)  H2(g) + ½O2(g) + → H2O(l) 
D)  Ti(s) + 2Cl2(g) → TiCl4(l) 
E)  ½H2(g) + ½ Cl2(g) → HCl(g) F) A) and B)
G) D) and E)

Question 18

A(n)___________ __________ is a process where heat is released to the surroundings.

Accepted Answer

The answer of A(n)___________ __________ is a process where heat...

Question 19

The highly exothermic thermite reaction,in which aluminum reduces iron(III) oxide to elemental iron,has been used by railroad repair crews to weld rails together. 2Al(s) + Fe2O3(s) → 2Fe(s) + Al2O3(s) ΔH°rxn = -847.6 kJ/mol
What mass of iron is formed if 725 kJ of heat are released?

Accepted Answer

A)  23.9 g
B)  47.8 g
C)  65.3 g
D)  95.5 g
E)  112 gF) A) and B)
G) All of the above

Question 20

Glycine,C2H5O2N,is important for biological energy.The combustion reaction of glycine is described by the following thermochemical equation. 4C2H5O2N(s) + 9O2(g) → 8CO2(g) + 10H2O(l) + 2N2(g) ΔH°rxn = -3896 kJ/mol
What is the standard enthalpy of formation of solid glycine?

Accepted Answer

A)  -51.90 kJ/mol
B)  -527.5 kJ/mol
C)  -974.0 kJ/mol
D)  -1502 kJ/mol
E)  -2476 kJ/molF) A) and B)
G) A) and C)

Exam 5: Thermochemistry

Ethylene glycol,used as a coolant in automotive engines,has a specific heat capacity of 2.42 J/g°C.Calculate q when 3.65 kg of ethylene glycol is cooled from 132°C to 85°C.

Correct Answer
verified

The sign of q when heat is absorbed by the system is ___________.

Correct Answer
verified

In an endothermic reaction,in going from the reactants to the products at the same temperature,the value of q is negative.

Correct Answer
verified

Cold packs,whose temperatures are lowered when ammonium nitrate dissolves in water,are carried by athletic trainers when transporting ice is not possible.Which of the following is true of this reaction?

Correct Answer
verified

An exothermic reaction causes the surroundings to

Correct Answer
verified

Correct Answer
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What is ΔH°_rxn for the reaction 2Al₂O₃(s) → 4Al(s) + 3O₂(g) ? ΔH°_f(Al₂O₃(s) ) = -1670 kJ/mol

Correct Answer
verified

Which relationship is always correct?

Correct Answer
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A system that does no work but which receives heat from the surroundings has

Correct Answer
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The work done on the surroundings by the expansion of a gas is w = -PΔV.

Correct Answer
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Using Hess's law,what is ΔH°_rxn for the following reaction? WO₃(s) + 3H₂(g) → W(s) + 3H₂O(g) 2W(s) + 3O₂(g) →2WO₃(s) ΔH°_rxn = -1685.8 kJ/mol 2H₂(g) + O₂(g) → 2H₂O(g) ΔH°_rxn = -483.6 kJ/mol

Correct Answer
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What is ΔH°_rxn for the following reaction? C₆H₆(l) + 15/2 O₂(g) → 6CO₂(g) + 3H₂O(l) 6C(graphite) + 3H₂(g) → C₆H₆(l) ΔH°_rxn = +49.0 kJ/mol C(graphite) + O₂(g) → CO₂(g) ΔH°_rxn = -393.5 kJ/mol H₂(g) + ½O₂(g) → H₂O(l) ΔH°_rxn = -285.8 kJ/mol

Correct Answer
verified

Which equation has a ΔH_rxn that is not equal to ΔH^o_f of the product? rev: 04_28_2015_QC_CS-14747

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

A(n)_ is a process where heat is released to the surroundings.

Correct Answer
verified

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

Correct Answer
verified

The highly exothermic thermite reaction,in which aluminum reduces iron(III) oxide to elemental iron,has been used by railroad repair crews to weld rails together. 2Al(s) + Fe₂O₃(s) → 2Fe(s) + Al₂O₃(s) ΔH°_rxn = -847.6 kJ/mol What mass of iron is formed if 725 kJ of heat are released?

Correct Answer
verified

A system initially has an internal energy U of 504 J.It undergoes a process during which it releases 111 J of heat energy to the surroundings,and does work of 222 J.What is the final energy of the system,in J?

Correct Answer
verified

Glycine,C₂H₅O₂N,is important for biological energy.The combustion reaction of glycine is described by the following thermochemical equation. 4C₂H₅O₂N(s) + 9O₂(g) → 8CO₂(g) + 10H₂O(l) + 2N₂(g) ΔH°_rxn = -3896 kJ/mol What is the standard enthalpy of formation of solid glycine?

Correct Answer
verified

Correct Answer
verified

Exam 5: Thermochemistry

Ethylene glycol,used as a coolant in automotive engines,has a specific heat capacity of 2.42 J/g°C.Calculate q when 3.65 kg of ethylene glycol is cooled from 132°C to 85°C.

Correct AnswerverifiedShow Answer

The sign of q when heat is absorbed by the system is ___________.

Correct AnswerverifiedShow Answer

In an endothermic reaction,in going from the reactants to the products at the same temperature,the value of q is negative.

Correct AnswerverifiedShow Answer

Cold packs,whose temperatures are lowered when ammonium nitrate dissolves in water,are carried by athletic trainers when transporting ice is not possible.Which of the following is true of this reaction?

Correct AnswerverifiedShow Answer

An exothermic reaction causes the surroundings to

Correct AnswerverifiedShow Answer

Correct AnswerverifiedShow Answer

What is ΔH°rxn for the reaction 2Al2O3(s) → 4Al(s) + 3O2(g) ? ΔH°f(Al2O3(s) ) = -1670 kJ/mol

Correct AnswerverifiedShow Answer

Which relationship is always correct?

Correct AnswerverifiedShow Answer

A system that does no work but which receives heat from the surroundings has

Correct AnswerverifiedShow Answer

The work done on the surroundings by the expansion of a gas is w = -PΔV.

Correct AnswerverifiedShow Answer

Using Hess's law,what is ΔH°rxn for the following reaction? WO3(s) + 3H2(g) → W(s) + 3H2O(g) 2W(s) + 3O2(g) →2WO3(s) ΔH°rxn = -1685.8 kJ/mol 2H2(g) + O2(g) → 2H2O(g) ΔH°rxn = -483.6 kJ/mol

Correct AnswerverifiedShow Answer

What is ΔH°rxn for the following reaction? C6H6(l) + 15/2 O2(g) → 6CO2(g) + 3H2O(l) 6C(graphite) + 3H2(g) → C6H6(l) ΔH°rxn = +49.0 kJ/mol C(graphite) + O2(g) → CO2(g) ΔH°rxn = -393.5 kJ/mol H2(g) + ½O2(g) → H2O(l) ΔH°rxn = -285.8 kJ/mol

Correct AnswerverifiedShow Answer

Which equation has a ΔHrxn that is not equal to ΔHof of the product? rev: 04_28_2015_QC_CS-14747

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

A(n)___________ __________ is a process where heat is released to the surroundings.

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

The highly exothermic thermite reaction,in which aluminum reduces iron(III) oxide to elemental iron,has been used by railroad repair crews to weld rails together. 2Al(s) + Fe2O3(s) → 2Fe(s) + Al2O3(s) ΔH°rxn = -847.6 kJ/mol What mass of iron is formed if 725 kJ of heat are released?

Correct AnswerverifiedShow Answer

A system initially has an internal energy U of 504 J.It undergoes a process during which it releases 111 J of heat energy to the surroundings,and does work of 222 J.What is the final energy of the system,in J?

Correct AnswerverifiedShow Answer

Glycine,C2H5O2N,is important for biological energy.The combustion reaction of glycine is described by the following thermochemical equation. 4C2H5O2N(s) + 9O2(g) → 8CO2(g) + 10H2O(l) + 2N2(g) ΔH°rxn = -3896 kJ/mol What is the standard enthalpy of formation of solid glycine?

Correct AnswerverifiedShow Answer

Correct AnswerverifiedShow Answer

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
verified

What is ΔH°_rxn for the reaction 2Al₂O₃(s) → 4Al(s) + 3O₂(g) ? ΔH°_f(Al₂O₃(s) ) = -1670 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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Using Hess's law,what is ΔH°_rxn for the following reaction? WO₃(s) + 3H₂(g) → W(s) + 3H₂O(g) 2W(s) + 3O₂(g) →2WO₃(s) ΔH°_rxn = -1685.8 kJ/mol 2H₂(g) + O₂(g) → 2H₂O(g) ΔH°_rxn = -483.6 kJ/mol

Correct Answer
verified

What is ΔH°_rxn for the following reaction? C₆H₆(l) + 15/2 O₂(g) → 6CO₂(g) + 3H₂O(l) 6C(graphite) + 3H₂(g) → C₆H₆(l) ΔH°_rxn = +49.0 kJ/mol C(graphite) + O₂(g) → CO₂(g) ΔH°_rxn = -393.5 kJ/mol H₂(g) + ½O₂(g) → H₂O(l) ΔH°_rxn = -285.8 kJ/mol

Correct Answer
verified

Which equation has a ΔH_rxn that is not equal to ΔH^o_f of the product? rev: 04_28_2015_QC_CS-14747

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

A(n)_ is a process where heat is released to the surroundings.

Correct Answer
verified

Correct Answer
verified

The highly exothermic thermite reaction,in which aluminum reduces iron(III) oxide to elemental iron,has been used by railroad repair crews to weld rails together. 2Al(s) + Fe₂O₃(s) → 2Fe(s) + Al₂O₃(s) ΔH°_rxn = -847.6 kJ/mol What mass of iron is formed if 725 kJ of heat are released?

Correct Answer
verified

Correct Answer
verified

Glycine,C₂H₅O₂N,is important for biological energy.The combustion reaction of glycine is described by the following thermochemical equation. 4C₂H₅O₂N(s) + 9O₂(g) → 8CO₂(g) + 10H₂O(l) + 2N₂(g) ΔH°_rxn = -3896 kJ/mol What is the standard enthalpy of formation of solid glycine?

Correct Answer
verified

Correct Answer
verified