Question 1

Calculate the ΔH°rxn for the following reaction. (ΔH°f [AsH3(g) ] = 66.4 kJ/mol; ΔH°f [H3AsO4(aq) ] = −904.6 kJ/mol; ΔH°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) B) and D)
G) A) and D)

Question 2

A system that undergoes an adiabatic change and does work on the surroundings has

Accepted Answer

A) w B) w > 0, Δ E > 0. C) w > 0, Δ E D) w 0. E) w < 0, Δ E < 0.F) All of the above G) C) and D)

Question 3

Sand is converted to pure silicon in a three step process. The third step is SiCl4(g)  + 2Mg(s)  → 2MgCl2(s)  + Si(s)  ΔH = −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 × 10 4 kJ
D)  −3.13 × 10 4 kJ
E)  None of these choices are correct.F) C) and E)
G) A) and B)

Question 4

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

Accepted Answer

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

Question 5

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)  ΔH = −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) None of the above
G) B) and C)

Question 6

A system delivers 1275 J of heat while the surroundings perform 855 J of work on it. Calculate ΔE in J.

Accepted Answer

A)  −2130 J
B)  −420 J
C)  420 J
D)  2130 J
E)  −1275 JF) B) and C)
G) A) and C)

Question 7

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

Accepted Answer

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

Question 8

In which of the following processes is ΔH = ΔE ?

Accepted Answer

A)  Two moles of ammonia gas are cooled from 325°C to 300°C at 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)  Calcium carbonate is heated to form calcium oxide and carbon dioxide in a container with variable volume.
E)  One mole of solid carbon dioxide sublimes to the gas phase.F) A) and E)
G) A) and D)

Question 9

The standard state of a substance in aqueous solution is a 1 M solution.

Accepted Answer

A) True 
 B)False

Question 10

A system initially has an internal energy E of 501 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)  168 J
B)  390 J
C)  612 J
D)  834 J
E)  This cannot be calculated without more information.F) A) and E)
G) D) and E)

Question 11

The standard heat (enthalpy) of formation of graphite is zero.

Accepted Answer

A) True 
 B)False

Question 12

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·K) )  for each substance is given in parentheses. Iron (0.450) , copper (0.387) , granite (0.79) , gold (0.129) , water (4.18) .

Accepted Answer

A)  Iron
B)  Copper
C)  Granite
D)  Gold
E)  WaterF) A) and C)
G) B) and E)

Question 13

Your favorite candy bar, Gummy Beakers, contains 1.2 × 106 J of energy while your favorite soft drink, Bolt, contains 6.7 × 105 J. If you eat two packs of Gummy Beakers a day and drink 3 cans of Bolt, what percent of your 2000 Calorie daily food intake is left for broccoli, beans, beef, etc.?

Accepted Answer

A)  53%
B)  47%
C)  27%
D)  11%
E)  0%F) A) and D)
G) None of the above

Question 14

An important step in the synthesis of nitric acid is the conversion of ammonia to nitric oxide. 4NH3(g)  + 5O2(g)  → 4NO(g)  + 6H2O(g) 
Calculate ΔH°rxn for this reaction.
ΔH°f [NH3(g) ] = −45.9 kJ/mol; ΔH°f [NO(g) ] = 90.3 kJ/mol; ΔH°f [H2O(g) ] = −241.8 kJ/mol

Accepted Answer

A)  −906.0 kJ
B)  −197.4 kJ
C)  −105.6 kJ
D)  197.4 kJ
E)  906.0 kJF) C) and E)
G) B) and E)

Question 15

ΔH does not depend on the path of a reaction, but ΔE does.

Accepted Answer

A) True 
 B)False

Question 16

Standard heats (enthalpies) of formation of compounds, ΔH°f, may be positive or negative.

Accepted Answer

A) True 
 B)False

Question 17

Benzene is a starting material in the synthesis of nylon fibers and polystyrene (styrofoam) . Its specific heat capacity is 1.74 J/(g·K) . If 16.7 kJ of energy is absorbed by a 225-g sample of benzene at 20.0°C, what is its final temperature?

Accepted Answer

A)  −22.7°C
B)  36.7°C
C)  42.7°C
D)  62.7°C
E)  None of these choices are correct.F) B) and C)
G) A) and D)

Question 18

The compound carbon suboxide, C3O2, is a gas at room temperature. Use the data supplied to calculate the heat of formation of carbon suboxide. (Data: 2CO(g)  + C(s)  → C3O2(g)  ΔH° = 127.3 kJ/mol
And: ΔHf° of CO(g)  = −110.5 kJ/mol)

Accepted Answer

A)  116.8
B)  −93.7
C)  227.8
D)  −348.3
E)  93.7F) A) and D)
G) A) and C)

Question 19

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)  Δ E = 0
B)  Δ H = 0
C)  Δ E > 0
D)  q = 0
E)  w = 0F) A) and C)
G) B) and C)

Question 20

A system expands from a volume of 1.00 L to 2.00 L against a constant external pressure of 1.00 atm. The work (w)  done by the system, in J, is

Accepted Answer

A)  1.00 J.
B)  2.00 J.
C)  1.01 × 10 2 J.
D)  1.01 × 10 5 J.
E)  None of these choices are correct.F) B) and C)
G) A) and E)

Exam 6: Thermochemistry: Energy Flow and Chemical Change

The compound carbon suboxide, C₃O₂, is a gas at room temperature. Use the data supplied to calculate the heat of formation of carbon suboxide. (Data: 2CO(g) + C(s) → C₃O₂(g) ΔH° = 127.3 kJ/mol And: ΔH_f° of CO(g) = −110.5 kJ/mol)

Correct Answer
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ΔH does not depend on the path of a reaction, but ΔE does.

Correct Answer
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In which of the following processes is ΔH = ΔE ?

Correct Answer
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Correct Answer
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A system that undergoes an adiabatic change and does work on the surroundings has

Correct Answer
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Calculate the ΔH°_rxnfor the following reaction. (ΔH°_f [AsH₃(g) ] = 66.4 kJ/mol; ΔH°_f [H₃AsO₄(aq) ] = −904.6 kJ/mol; ΔH°_f [H₂O(l) ] = −285.8 kJ/mol) H₃AsO₄(aq) + 4H₂(g) → AsH₃(g) + 4H₂O(l)

Correct Answer
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Correct Answer
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The standard state of a substance in aqueous solution is a 1 M solution.

Correct Answer
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An important step in the synthesis of nitric acid is the conversion of ammonia to nitric oxide. 4NH₃(g) + 5O₂(g) → 4NO(g) + 6H₂O(g) Calculate ΔH°_rxnfor this reaction. ΔH°_f [NH₃(g) ] = −45.9 kJ/mol; ΔH°_f [NO(g) ] = 90.3 kJ/mol; ΔH°_f [H₂O(g) ] = −241.8 kJ/mol

Correct Answer
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Your favorite candy bar, Gummy Beakers, contains 1.2 × 10⁶ J of energy while your favorite soft drink, Bolt, contains 6.7 × 10⁵J. If you eat two packs of Gummy Beakers a day and drink 3 cans of Bolt, what percent of your 2000 Calorie daily food intake is left for broccoli, beans, beef, etc.?

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

Correct Answer
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A system initially has an internal energy E of 501 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
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A system expands from a volume of 1.00 L to 2.00 L against a constant external pressure of 1.00 atm. The work (w) done by the system, in J, is

Correct Answer
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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) ΔH = −827.4 kJ What mass of galena is converted to lead oxide if 975 kJ of heat are liberated?

Correct Answer
verified

Benzene is a starting material in the synthesis of nylon fibers and polystyrene (styrofoam) . Its specific heat capacity is 1.74 J/(g·K) . If 16.7 kJ of energy is absorbed by a 225-g sample of benzene at 20.0°C, what is its final temperature?

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

Correct Answer
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A system delivers 1275 J of heat while the surroundings perform 855 J of work on it. Calculate ΔE in J.

Correct Answer
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Standard heats (enthalpies) of formation of compounds, ΔH°_f, may be positive or negative.

Correct Answer
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The standard heat (enthalpy) of formation of graphite is zero.

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

Correct Answer
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Exam 6: Thermochemistry: Energy Flow and Chemical Change

The compound carbon suboxide, C3O2, is a gas at room temperature. Use the data supplied to calculate the heat of formation of carbon suboxide. (Data: 2CO(g) + C(s) → C3O2(g) ΔH° = 127.3 kJ/mol And: ΔHf° of CO(g) = −110.5 kJ/mol)

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ΔH does not depend on the path of a reaction, but ΔE does.

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In which of the following processes is ΔH = ΔE ?

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Correct AnswerverifiedShow Answer

A system that undergoes an adiabatic change and does work on the surroundings has

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

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Correct AnswerverifiedShow Answer

The standard state of a substance in aqueous solution is a 1 M solution.

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An important step in the synthesis of nitric acid is the conversion of ammonia to nitric oxide. 4NH3(g) + 5O2(g) → 4NO(g) + 6H2O(g) Calculate ΔH°rxn for this reaction. ΔH°f [NH3(g) ] = −45.9 kJ/mol; ΔH°f [NO(g) ] = 90.3 kJ/mol; ΔH°f [H2O(g) ] = −241.8 kJ/mol

Correct AnswerverifiedShow Answer

Your favorite candy bar, Gummy Beakers, contains 1.2 × 106 J of energy while your favorite soft drink, Bolt, contains 6.7 × 105 J. If you eat two packs of Gummy Beakers a day and drink 3 cans of Bolt, what percent of your 2000 Calorie daily food intake is left for broccoli, beans, beef, etc.?

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

Correct AnswerverifiedShow Answer

A system initially has an internal energy E of 501 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

A system expands from a volume of 1.00 L to 2.00 L against a constant external pressure of 1.00 atm. The work (w) done by the system, in J, is

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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) ΔH = −827.4 kJ What mass of galena is converted to lead oxide if 975 kJ of heat are liberated?

Correct AnswerverifiedShow Answer

Benzene is a starting material in the synthesis of nylon fibers and polystyrene (styrofoam) . Its specific heat capacity is 1.74 J/(g·K) . If 16.7 kJ of energy is absorbed by a 225-g sample of benzene at 20.0°C, what is its final temperature?

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

A system delivers 1275 J of heat while the surroundings perform 855 J of work on it. Calculate ΔE in J.

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Standard heats (enthalpies) of formation of compounds, ΔH°f, may be positive or negative.

Correct AnswerverifiedShow Answer

The standard heat (enthalpy) of formation of graphite is zero.

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) ΔH = −625.6 kJ What is the enthalpy change when 25.0 mol of silicon tetrachloride is converted to elemental silicon?

Correct AnswerverifiedShow Answer

The compound carbon suboxide, C₃O₂, is a gas at room temperature. Use the data supplied to calculate the heat of formation of carbon suboxide. (Data: 2CO(g) + C(s) → C₃O₂(g) ΔH° = 127.3 kJ/mol And: ΔH_f° of CO(g) = −110.5 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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Calculate the ΔH°_rxnfor the following reaction. (ΔH°_f [AsH₃(g) ] = 66.4 kJ/mol; ΔH°_f [H₃AsO₄(aq) ] = −904.6 kJ/mol; ΔH°_f [H₂O(l) ] = −285.8 kJ/mol) H₃AsO₄(aq) + 4H₂(g) → AsH₃(g) + 4H₂O(l)

Correct Answer
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Correct Answer
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Correct Answer
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An important step in the synthesis of nitric acid is the conversion of ammonia to nitric oxide. 4NH₃(g) + 5O₂(g) → 4NO(g) + 6H₂O(g) Calculate ΔH°_rxnfor this reaction. ΔH°_f [NH₃(g) ] = −45.9 kJ/mol; ΔH°_f [NO(g) ] = 90.3 kJ/mol; ΔH°_f [H₂O(g) ] = −241.8 kJ/mol

Correct Answer
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Your favorite candy bar, Gummy Beakers, contains 1.2 × 10⁶ J of energy while your favorite soft drink, Bolt, contains 6.7 × 10⁵J. If you eat two packs of Gummy Beakers a day and drink 3 cans of Bolt, what percent of your 2000 Calorie daily food intake is left for broccoli, beans, beef, etc.?

Correct Answer
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Correct Answer
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Correct Answer
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Correct Answer
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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) ΔH = −827.4 kJ What mass of galena is converted to lead oxide if 975 kJ of heat are liberated?

Correct Answer
verified

Correct Answer
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Correct Answer
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Correct Answer
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Standard heats (enthalpies) of formation of compounds, ΔH°_f, may be positive or negative.

Correct Answer
verified

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

Correct Answer
verified