Question 1

A system contracts from an initial volume of 15.0 L to a final volume of 10.0 L under a constant external pressure of 0.800 atm. The value of w, in J, is

Accepted Answer

A)   -4.0 J.
B)   4.0 J.
C)   -405 J.
D)   405 J.
E)   4.05 × 103 J.F) A) and D)
G) B) and D) D

Question 2

Galena is the ore from which elemental lead is extracted. In the first step of the extraction process, galena is heated in air to form lead(II)  oxide.
 2PbS(s)  + 3O2(g)   2PbO(s)  + 2SO2(g)  H = -827.4 kJ
What mass of galena is converted to lead oxide if 975 kJ of heat are liberated?

Accepted Answer

A)   203 g
B)   282 g
C)   406 g
D)   478 g
E)   564 gF) A) and B)
G) D) and E)

Question 3

A backpacker collects snow at 0°C, and places it in a cooking pot on a camp stove. It takes 643 kJ of heat energy to melt the snow and bring the water to boiling. Assuming no heat loss, and neglecting the specific heat capacity of the pot, calculate the mass of snow that the backpacker collected. (Data: specific heat capacity of liquid water, c = 4.18 J/gK; and: H2O(s)   H2O(l)  H = Hfusion = 6.02 kJ/mol)

Accepted Answer

A)   1.92 kg
B)   1.90 kg
C)   1.52 kg
D)   855 g
E)   < 800 gF) B) and E)
G) All of the above

Question 4

For a reaction in a sealed, rigid container, F1F1F1S1F1F1F10H is always greater than F1F1F1S1F1F1F10E.

Accepted Answer

A) True 
 B)False

Question 5

a. Explain fully what is meant by the term "state function."
b. (i) Give two examples of thermodynamic quantities which state functions.
(ii) Give two examples of thermodynamic quantities which are not state functions.

Accepted Answer

a. A state function depends on...

Question 6

Different chemical bonds have different potential energies.

Accepted Answer

A) True 
 B)False

Question 7

A common laboratory reaction is the neutralization of an acid with a base. When 50.0 mL of 0.500 M HCl at 25.0°C is added to 50.0 mL of 0.500 M NaOH at 25.0°C in a coffee cup calorimeter, the temperature of the mixture rises to 28.2°C. What is the heat of reaction per mole of acid? Assume the mixture has a specific heat capacity of 4.18 J/(g·K)  and that the densities of the reactant solutions are both 1.00 g/mL.

Accepted Answer

A)   670 J
B)   1300 J
C)   27 kJ
D)   54 kJ
E)   > 100 kJF) C) and D)
G) C) and E)

Question 8

Calculate the H°rxn for the following reaction. (H°f [AsH3(g) ] = 66.4 kJ/mol; H°f [H3AsO4(aq) ] = -904.6 kJ/mol; H°f [H2O(l) ] = -285.8 kJ/mol)  
H3AsO4(aq)  + 4H2(g)   AsH3(g)  + 4H2O(l)

Accepted Answer

A)   -1981.4 kJ
B)   -685.2 kJ
C)   -172.2 kJ
D)   172.2 kJ
E)   685.2 kJF) A) and C)
G) C) and D)

Question 9

For which one of the following reactions will H be approximately (or exactly)  equal to E?

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) D) and E)
G) A) and E)

Question 10

In which one of the following reactions would you expect H to be substantially greater than E (i.e., H > E) ?

Accepted Answer

A)   H2(g)  + Br2(g)   2HBr(g) 
B)   CO2(s)   CO2(g) 
C)   C2H2(g)  + H2(g)   C2H4(g) 
D)   H2O(s)   H2O(l) 
E)   HCl(aq)  + NaOH(aq)   NaCl(aq)  + H2O(l) F) B) and E)
G) A) and B)

Question 11

Two solutions (the system) , each of 25.0 mL volume and at 25.0°C, are mixed in a beaker. A reaction occurs between them, and the temperature rises to 35.0°C. After the products have equilibrated with the surroundings, the temperature is again 25.0°C and the total volume is 50.0 mL. No gases are involved in the reaction. Which one of the following relationships concerning the change from initial to final states (both at 25.0°C)  is correct?

Accepted Answer

A)   .E = 0
B)   .H = 0
C)   .E > 0
D)   q = 0
E)   w = 0F) None of the above
G) A) and D)

Question 12

Consider the equation F1F1F1S1F1F1F10E = q + w
Explain fully the meaning of all three terms in the equation, and also the implied sign convention for q and w.

Accepted Answer

E is the internal energy of a system, i.e., the total energy of all forms of energy in the system. So, F1F1F1S1F1F1F10E is the change internal energy of the system; q is heat transferred to or from the system, w is work done on or by the system. The sign convention is that q and w are positive when the system gains energy; i.e., heat transferred to the system, or work done on the system, are both positive.

Question 13

A Snickers® candy bar contains 280 Calories, of which the fat content accounts for 120 Calories. What is the energy of the fat content, in kJ?

Accepted Answer

A)   5.0 × 10-1 kJ
B)   29 kJ
C)   5.0 × 102 kJ
D)   1.2 × 103 kJ
E)   5.0 × 105 kJF) None of the above
G) A) and C)

Question 14

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)  H = -850 kJ
What mass of iron is formed when 725 kJ of heat are released?

Accepted Answer

A)   47 g
B)   65 g
C)   95 g
D)   112 g
E)   130 gF) A) and B)
G) None of the above

Question 15

Sand is converted to pure silicon in a three step process. The third step is 
SiCl4(g)  + 2Mg(s)   2MgCl2(s)  + Si(s)  H = -625.6 kJ
What is the enthalpy change when 25.0 mol of silicon tetrachloride is converted to elemental silicon?

Accepted Answer

A)   -25.0 kJ
B)   -7820 kJ
C)   -1.56 × 104 kJ
D)   -3.13 × 104 kJ
E)   none of the aboveF) B) and C)
G) C) and D)

Question 16

Stoichiometric amounts of nitrogen gas and hydrogen gas react in a calorimeter to produce 5.00 g of ammonia gas. The calorimeter temperature rises 0.42°C. The calorimeter and water have a combined heat capacity of 32.16 kJ/K. Calculate the heat of formation of ammonia, Hf°, in kJ/mol. The formation reaction for ammonia is: 0.5N2(g)  + 1.5H2(g)   NH3(g) .

Accepted Answer

A)   -46 kJ/mol
B)   -13.5 kJ/mol
C)   -3.97 kJ/mol
D)   3.97 kJ/mol
E)   13.5 kJ/molF) A) and E)
G) A) and D)

Question 17

Calculate the H°rxn for the following reaction. (H°f [SiO2(s) ] = -910.9 kJ/mol; H°f [SiCl4(g) ] = -657.0 kJ/mol; H°f [HCl(g) ] = -92.3 kJ/mol; H°f [H2O (g) ] = -241.8 kJ/mol)  SiO2(s)  + 4HCl(g)   SiCl4(g)  + 2H2O(g)

Accepted Answer

A)   -139.5 kJ
B)   -137.4 kJ
C)   -104.4 kJ
D)   104.4 kJ
E)   139.5 kJF) A) and B)
G) A) and D)

Question 18

A system that does no work but which transfers heat to the surroundings has

Accepted Answer

A)   q E > 0.
B)   q E 
C)   q > 0, E > 0.
D)   q > 0, E 
E)   q E = 0.F) D) and E)
G) A) and E) B

Question 19

Calculate, in J, the work done by 10.0 g of CO2 when it sublimes against a pressure of 1.00 atm to form gaseous CO2 at 0.0°C. The volume of CO2(s) can be neglected; CO2(g) can be assumed to behave ideally. The process occurring is
CO2(s) F1F1F1S1F1F1F10 CO2(g)

Accepted Answer

a. <font face="symbol"></font>E...

Question 20

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

Exam 6: Thermochemistry: Energy Flow and Chemical Change

A system contracts from an initial volume of 15.0 L to a final volume of 10.0 L under a constant external pressure of 0.800 atm. The value of w, in J, is

Correct Answer
verified
D

Galena is the ore from which elemental lead is extracted. In the first step of the extraction process, galena is heated in air to form lead(II) oxide. 2PbS(s) + 3O₂(g)  2PbO(s) + 2SO₂(g) H = -827.4 kJ What mass of galena is converted to lead oxide if 975 kJ of heat are liberated?

Correct Answer
verified

Correct Answer
verified

For a reaction in a sealed, rigid container, H is always greater than E.

Correct Answer
verified

a. Explain fully what is meant by the term "state function." b. (i) Give two examples of thermodynamic quantities which state functions. (ii) Give two examples of thermodynamic quantities which are not state functions.

Correct Answer
verified
a. A state function depends on...
View Answer

Different chemical bonds have different potential energies.

Correct Answer
verified

Correct Answer
verified

Calculate the H°_rxn for the following reaction. (H°_f [AsH₃(g) ] = 66.4 kJ/mol; H°_f [H₃AsO₄(aq) ] = -904.6 kJ/mol; H°_f [H₂O(l) ] = -285.8 kJ/mol) H₃AsO₄(aq) + 4H₂(g)  AsH₃(g) + 4H₂O(l)

Correct Answer
verified

For which one of the following reactions will H be approximately (or exactly) equal to E?

Correct Answer
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In which one of the following reactions would you expect H to be substantially greater than E (i.e., H > E) ?

Correct Answer
verified

Correct Answer
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Consider the equation E = q + w Explain fully the meaning of all three terms in the equation, and also the implied sign convention for q and w.

A Snickers^® candy bar contains 280 Calories, of which the fat content accounts for 120 Calories. What is the energy of the fat content, in kJ?

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) H = -850 kJ What mass of iron is formed when 725 kJ of heat are released?

Correct Answer
verified

Sand is converted to pure silicon in a three step process. The third step is SiCl₄(g) + 2Mg(s)  2MgCl₂(s) + Si(s) H = -625.6 kJ What is the enthalpy change when 25.0 mol of silicon tetrachloride is converted to elemental silicon?

Correct Answer
verified

Correct Answer
verified

Calculate the H°_rxn for the following reaction. (H°_f [SiO₂(s) ] = -910.9 kJ/mol; H°_f [SiCl₄(g) ] = -657.0 kJ/mol; H°_f [HCl(g) ] = -92.3 kJ/mol; H°_f [H₂O (g) ] = -241.8 kJ/mol) SiO₂(s) + 4HCl(g)  SiCl₄(g) + 2H₂O(g)

Correct Answer
verified

A system that does no work but which transfers heat to the surroundings has

Correct Answer
verified
B

Calculate, in J, the work done by 10.0 g of CO₂ when it sublimes against a pressure of 1.00 atm to form gaseous CO₂ at 0.0°C. The volume of CO₂(s) can be neglected; CO₂(g) can be assumed to behave ideally. The process occurring is CO₂(s)  CO₂(g)

Correct Answer
verified
a. E...
View Answer

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

Exam 6: Thermochemistry: Energy Flow and Chemical Change

A system contracts from an initial volume of 15.0 L to a final volume of 10.0 L under a constant external pressure of 0.800 atm. The value of w, in J, is

Correct AnswerverifiedD

Galena is the ore from which elemental lead is extracted. In the first step of the extraction process, galena is heated in air to form lead(II) oxide. 2PbS(s) + 3O2(g)  2PbO(s) + 2SO2(g) H = -827.4 kJ What mass of galena is converted to lead oxide if 975 kJ of heat are liberated?

Correct AnswerverifiedShow Answer

Correct AnswerverifiedShow Answer

For a reaction in a sealed, rigid container, H is always greater than E.

Correct AnswerverifiedShow Answer

a. Explain fully what is meant by the term "state function." b. (i) Give two examples of thermodynamic quantities which state functions. (ii) Give two examples of thermodynamic quantities which are not state functions.

Correct Answerverifieda. A state function depends on...View AnswerShow Answer

Different chemical bonds have different potential energies.

Correct AnswerverifiedShow Answer

Correct AnswerverifiedShow Answer

Calculate the H°rxn for the following reaction. (H°f [AsH3(g) ] = 66.4 kJ/mol; H°f [H3AsO4(aq) ] = -904.6 kJ/mol; H°f [H2O(l) ] = -285.8 kJ/mol) H3AsO4(aq) + 4H2(g)  AsH3(g) + 4H2O(l)

Correct AnswerverifiedShow Answer

For which one of the following reactions will H be approximately (or exactly) equal to E?

Correct AnswerverifiedShow Answer

In which one of the following reactions would you expect H to be substantially greater than E (i.e., H > E) ?

Correct AnswerverifiedShow Answer

Correct AnswerverifiedShow Answer

Consider the equation E = q + w Explain fully the meaning of all three terms in the equation, and also the implied sign convention for q and w.

A Snickers® candy bar contains 280 Calories, of which the fat content accounts for 120 Calories. What is the energy of the fat content, in kJ?

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) H = -850 kJ What mass of iron is formed when 725 kJ of heat are released?

Correct AnswerverifiedShow Answer

Sand is converted to pure silicon in a three step process. The third step is SiCl4(g) + 2Mg(s)  2MgCl2(s) + Si(s) H = -625.6 kJ What is the enthalpy change when 25.0 mol of silicon tetrachloride is converted to elemental silicon?

Correct AnswerverifiedShow Answer

Correct AnswerverifiedShow Answer

Calculate the H°rxn for the following reaction. (H°f [SiO2(s) ] = -910.9 kJ/mol; H°f [SiCl4(g) ] = -657.0 kJ/mol; H°f [HCl(g) ] = -92.3 kJ/mol; H°f [H2O (g) ] = -241.8 kJ/mol) SiO2(s) + 4HCl(g)  SiCl4(g) + 2H2O(g)

Correct AnswerverifiedShow Answer

A system that does no work but which transfers heat to the surroundings has

Correct AnswerverifiedB

Calculate, in J, the work done by 10.0 g of CO2 when it sublimes against a pressure of 1.00 atm to form gaseous CO2 at 0.0°C. The volume of CO2(s) can be neglected; CO2(g) can be assumed to behave ideally. The process occurring is CO2(s)  CO2(g)

Correct Answerverifieda. E...View AnswerShow 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

Correct Answer
verified
D

Galena is the ore from which elemental lead is extracted. In the first step of the extraction process, galena is heated in air to form lead(II) oxide. 2PbS(s) + 3O₂(g)  2PbO(s) + 2SO₂(g) H = -827.4 kJ What mass of galena is converted to lead oxide if 975 kJ of heat are liberated?

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified
a. A state function depends on...
View Answer

Correct Answer
verified

Correct Answer
verified

Calculate the H°_rxn for the following reaction. (H°_f [AsH₃(g) ] = 66.4 kJ/mol; H°_f [H₃AsO₄(aq) ] = -904.6 kJ/mol; H°_f [H₂O(l) ] = -285.8 kJ/mol) H₃AsO₄(aq) + 4H₂(g)  AsH₃(g) + 4H₂O(l)

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

A Snickers^® candy bar contains 280 Calories, of which the fat content accounts for 120 Calories. What is the energy of the fat content, in kJ?

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) H = -850 kJ What mass of iron is formed when 725 kJ of heat are released?

Correct Answer
verified

Sand is converted to pure silicon in a three step process. The third step is SiCl₄(g) + 2Mg(s)  2MgCl₂(s) + Si(s) H = -625.6 kJ What is the enthalpy change when 25.0 mol of silicon tetrachloride is converted to elemental silicon?

Correct Answer
verified

Correct Answer
verified

Calculate the H°_rxn for the following reaction. (H°_f [SiO₂(s) ] = -910.9 kJ/mol; H°_f [SiCl₄(g) ] = -657.0 kJ/mol; H°_f [HCl(g) ] = -92.3 kJ/mol; H°_f [H₂O (g) ] = -241.8 kJ/mol) SiO₂(s) + 4HCl(g)  SiCl₄(g) + 2H₂O(g)

Correct Answer
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Correct Answer
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B

Calculate, in J, the work done by 10.0 g of CO₂ when it sublimes against a pressure of 1.00 atm to form gaseous CO₂ at 0.0°C. The volume of CO₂(s) can be neglected; CO₂(g) can be assumed to behave ideally. The process occurring is CO₂(s)  CO₂(g)

Correct Answer
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a. E...
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Correct Answer
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