Question 1

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

Accepted Answer

A) w 0, Δ E > 0. C) w > 0, Δ E 0. E) w < 0, Δ E < 0. A) w 0, Δ E > 0. C) w > 0, Δ E 0. E) w < 0, Δ E < 0.

Question 2

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

Accepted Answer

A) True 
 B)False

Question 3

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 J 
A) −2130 J 
B) −420 J 
C) 420 J 
D) 2130 J 
E) −1275 J

Question 4

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 kJ 
A) −906.0 kJ 
B) −197.4 kJ 
C) −105.6 kJ 
D) 197.4 kJ 
E) 906.0 kJ

Question 5

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) 93.7 
A) 116.8 
B) −93.7 
C) 227.8 
D) −348.3 
E) 93.7

Question 6

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

Question 7

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

Accepted Answer

A) q 0. B) q 0, Δ E > 0. D) q > 0, Δ E < 0. E) q < 0, Δ E = 0. A) q 0. B) q 0, Δ E > 0. D) q > 0, Δ E < 0. E) q < 0, Δ E = 0.

Question 8

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 kJ 
A) −1981.4 kJ 
B) −685.2 kJ 
C) −172.2 kJ 
D) 172.2 kJ 
E) 685.2 kJ

Question 9

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

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. 
A) 168 J 
B) 390 J 
C) 612 J 
D) 834 J 
E) This cannot be calculated without more information.

Question 11

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. 
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.

Question 12

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% 
A) 53% 
B) 47% 
C) 27% 
D) 11% 
E) 0%

Question 13

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

Accepted Answer

A) True 
 B)False

Question 14

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

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) 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. 
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.

Question 16

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) Water 
A) Iron 
B) Copper 
C) Granite 
D) Gold 
E) Water

Question 17

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

Accepted Answer

A) True 
 B)False

Question 18

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

Accepted Answer

A) q 0. B) q > 0, Δ E < 0. C) q = Δ E. D) q = −Δ E. E) w = Δ E. A) q 0. B) q > 0, Δ E < 0. C) q = Δ E. D) q = −Δ E. E) w = Δ E.

Question 19

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

Accepted Answer

A) True 
 B)False

Question 20

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. 
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.

Exam 6: Thermochemistry: Energy Flow and Chemical Change

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

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

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

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

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)

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?

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

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)

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?

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?

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

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.?

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

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?

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

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

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

In which of the following processes is ΔH = ΔE ?

Keys to the Study of Chemistry: Definitions, Units, and Problem Solving

The Components of Matter

Stoichiometry of Formulas and Equations

Three Major Classes of Chemical Reactions

Gases and the Kinetic-Molecular Theory

Quantum Theory and Atomic Structure

Electron Configuration and Chemical Periodicity

Models of Chemical Bonding

The Shapes of Molecules

Theories of Covalent Bonding

Intermolecular Forces: Liquids, Solids, and Phase Changes

The Properties of Mixtures: Solutions and Colloids

Periodic Patterns in the Main-Group Elements

Organic Compounds and the Atomic Properties of Carbon

Kinetics: Rates and Mechanisms of Chemical Reactions

Equilibrium: the Extent of Chemical Reactions

Acid-Base Equilibria

Ionic Equilibria in Aqueous Systems

Thermodynamics: Entropy, Free Energy, and Reaction Direction

Electrochemistry: Chemical Change and Electrical Work

The Elements in Nature and Industry

Transition Elements and Their Coordination Compounds

Nuclear Reactions and Their Applications

Filters

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

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)

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?

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)

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.?

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

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?