Ch.6 – Thermochemistry Energy Flow And | Test Bank + Answers

Chapter 6 Test Bank

Thermochemistry: Energy Flow and Chemical Change

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

A. q < 0, ΔE > 0.

B. q < 0, ΔE < 0.

C. q > 0, ΔE > 0.

D. q > 0, ΔE < 0.

E. q < 0, ΔE = 0.

Accessibility: Keyboard Navigation

Bloom's: 2. Understand

Difficulty: Easy

Gradable: automatic

Subtopic: System/Surroundings and Heat/Work

Topic: Thermochemistry

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

A. q < 0, ΔE > 0.

B. q > 0, ΔE < 0.

C. q = ΔE.

D. q = –ΔE.

E. w = ΔE.

Accessibility: Keyboard Navigation

Bloom's: 2. Understand

Difficulty: Easy

Gradable: automatic

Subtopic: System/Surroundings and Heat/Work

Topic: Thermochemistry

3. A system that undergoes an adiabatic change (i.e., q = 0) and does work on the surroundings has

A. w < 0, ΔE = 0.

B. w > 0, ΔE > 0.

C. w > 0, ΔE < 0.

D. w < 0, ΔE > 0.

E. w < 0, ΔE < 0.

Accessibility: Keyboard Navigation

Bloom's: 2. Understand

Difficulty: Easy

Gradable: automatic

Subtopic: System/Surroundings and Heat/Work

Topic: Thermochemistry

4. A system that undergoes an adiabatic change (i.e., q = 0) and has work done on it by the surroundings has

A. w = ΔE.

B. w = –ΔE.

C. w > 0, ΔE < 0.

D. w < 0, ΔE > 0.

E. w > ΔE.

Accessibility: Keyboard Navigation

Bloom's: 2. Understand

Difficulty: Easy

Gradable: automatic

Subtopic: System/Surroundings and Heat/Work

Topic: Thermochemistry

5. A system receives 575 J of heat and delivers 425 J of work. Calculate the change in the internal energy, ΔE, of the system.

A. –150 J

B. 150 J

C. –l000 J

D. 1000 J

E. 575 J

Accessibility: Keyboard Navigation

Bloom's: 3. Apply

Difficulty: Easy

Gradable: automatic

Subtopic: First Law of Thermodynamics (Conservation of Energy)

Topic: Thermochemistry

6. A system delivers 225 J of heat to the surroundings while delivering 645 J of work. Calculate the change in the internal energy, ΔE, of the system.

A. –420 J

B. 420 J

C. –870 J

D. 870 J

E. –225 J

Accessibility: Keyboard Navigation

Bloom's: 3. Apply

Difficulty: Easy

Gradable: automatic

Subtopic: First Law of Thermodynamics (Conservation of Energy)

Topic: Thermochemistry

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

A. –2130 J

B. –420 J

C. 420 J

D. 2130 J

E. –1275 J

Accessibility: Keyboard Navigation

Bloom's: 3. Apply

Difficulty: Easy

Gradable: automatic

Subtopic: First Law of Thermodynamics (Conservation of Energy)

Topic: Thermochemistry

8. A system absorbs 21.6 kJ of heat while performing 6.9 kJ of work on the surroundings. If the initial internal energy, E, is 61.2 kJ, what is the final value of E?

A. 32.7 kJ

B. 46.5 kJ

C. 75.9 kJ

D. 82.8 kJ

E. 89.7 kJ

Accessibility: Keyboard Navigation

Bloom's: 3. Apply

Difficulty: Easy

Gradable: automatic

Subtopic: First Law of Thermodynamics (Conservation of Energy)

Topic: Thermochemistry

9. 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. 168 J

B. 390 J

C. 612 J

D. 834 J

E. This cannot be calculated without more information.

Accessibility: Keyboard Navigation

Bloom's: 3. Apply

Difficulty: Medium

Gradable: automatic

Subtopic: First Law of Thermodynamics (Conservation of Energy)

Topic: Thermochemistry

10. 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

A. 1.00 J.

B. 2.00 J.

C. 1.01 × 10² J.

D. 1.01 × 10⁵ J.

E. None of these choices are correct.

Accessibility: Keyboard Navigation

Bloom's: 3. Apply

Difficulty: Medium

Gradable: automatic

Subtopic: System/Surroundings and Heat/Work

Topic: Thermochemistry

11. 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

A. –4.0 J.

B. 4.0 J.

C. –405 J.

D. 405 J.

E. 4.05 × 10³ J.

Accessibility: Keyboard Navigation

Bloom's: 3. Apply

Difficulty: Medium

Gradable: automatic

Subtopic: System/Surroundings and Heat/Work

Topic: Thermochemistry

12. An ideal gas (the system) is contained in a flexible balloon at a pressure of 1 atm and is initially at a temperature of 20.°C. The surrounding air is at the same pressure, but its temperature is 25°C. When the system has equilibrated with its surroundings, both systems and surroundings are at 25°C and 1 atm. In changing from the initial to the final state, which one of the following relationships regarding the system is correct?

A. ΔE < 0

B. ΔE = 0

C. ΔH = 0

D. w > 0

E. q > 0

Accessibility: Keyboard Navigation

Bloom's: 2. Understand

Difficulty: Hard

Gradable: automatic

Subtopic: System/Surroundings and Heat/Work

Topic: Thermochemistry

13. Which one of the following relationships is always correct?

A. potential energy + kinetic energy = constant

B. E = q + w

C. ΔE = ΔH – PΔV

D. H = E + PV

E. ΔH = q_v

Accessibility: Keyboard Navigation

Bloom's: 1. Remember

Difficulty: Easy

Gradable: automatic

Subtopic: First Law of Thermodynamics (Conservation of Energy)

Topic: Thermochemistry

14. In which of the following processes is ΔH = ΔE ?

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.

Accessibility: Keyboard Navigation

Bloom's: 2. Understand

Difficulty: Medium

Gradable: automatic

Subtopic: First Law of Thermodynamics (Conservation of Energy)

Topic: Thermochemistry

15. For which one of the following reactions will ΔH be approximately (or exactly) equal to ΔE?

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)

Accessibility: Keyboard Navigation

Bloom's: 2. Understand

Difficulty: Medium

Gradable: automatic

Subtopic: First Law of Thermodynamics (Conservation of Energy)

Topic: Thermochemistry

16. In which one of the following reactions would you expect ΔH to be substantially greater than ΔE (i.e., ΔH > ΔE)?

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)

Accessibility: Keyboard Navigation

Bloom's: 2. Understand

Difficulty: Medium

Gradable: automatic

Subtopic: First Law of Thermodynamics (Conservation of Energy)

Topic: Thermochemistry

17. 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?

A. ΔH < 0, process is exothermic

B. ΔH > 0, process is exothermic

C. ΔH < 0, process is endothermic

D. ΔH > 0, process is endothermic

E. ΔH = 0, since cold packs are sealed

Accessibility: Keyboard Navigation

Bloom's: 2. Understand

Difficulty: Easy

Gradable: automatic

Subtopic: Enthalpy (Heats of Reaction)

Topic: Thermochemistry

18. In a phase change of water between the liquid and the gas phases, 770.1 kJ of energy was released by the system. What was the product, and how much of it was formed in the phase change?

(Data: H₂O(l) → H₂O(g) ΔH = 44.01 kJ/mol.)

A. 315 g water vapor was produced.

B. 17.5 g of water vapor was produced.

C. 17.5 mol of water vapor was produced.

D. 17.5 mol of liquid water was produced.

E. 17.5 g of liquid water was produced.

Accessibility: Keyboard Navigation

Bloom's: 3. Apply

Difficulty: Medium

Gradable: automatic

Subtopic: Enthalpy (Heats of Reaction)

Topic: Thermochemistry

19. The dissolution of barium hydroxide in water is an exothermic process. Which of the following statements is correct?

A. The enthalpy of solid barium hydroxide plus pure water is less than that of the solution, at the same temperature.

B. The enthalpy of solid barium hydroxide plus pure water is greater than that of the solution, at the same temperature.

C. The enthalpy of solid barium hydroxide plus pure water is the same as that of the solution, at the same temperature.

D. The temperature of the solution is lower than of the barium hydroxide and water before mixing.

E. When barium hydroxide dissolves in water, the system does work on the surroundings.

Accessibility: Keyboard Navigation

Bloom's: 2. Understand

Difficulty: Medium

Gradable: automatic

Subtopic: Enthalpy (Heats of Reaction)

Topic: Thermochemistry

20. 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?

A. ΔE = 0

B. ΔH = 0

C. ΔE > 0

D. q = 0

E. w = 0

Accessibility: Keyboard Navigation

Bloom's: 2. Understand

Difficulty: Hard

Gradable: automatic

Subtopic: Enthalpy (Heats of Reaction)

Topic: Thermochemistry

21. 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?

A. 5.0 × 10^–1 kJ

B. 29 kJ

C. 5.0 × 10² kJ

D. 1.2 × 10³ kJ

E. 5.0 × 10⁵ kJ

Accessibility: Keyboard Navigation

Bloom's: 3. Apply

Difficulty: Easy

Gradable: automatic

Subtopic: Units of Energy

Topic: Thermochemistry

22. 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.?

A. 53%

B. 47%

C. 27%

D. 11%

E. 0%

Accessibility: Keyboard Navigation

Bloom's: 3. Apply

Difficulty: Medium

Gradable: automatic

Subtopic: Units of Energy

Topic: Thermochemistry

23. Natural gas, or methane, is an important fuel. Combustion of one mole of methane releases 802.3 kilojoules of energy. How much energy does that represent in kilocalories?

A. 1.92 × 10^–1 kcal

B. 1.92 × 10² kcal

C. 3.36 × 10³ kcal

D. 1.92 × 10⁵ kcal

E. 3.36 × 10⁶ kcal

Accessibility: Keyboard Navigation

Bloom's: 3. Apply

Difficulty: Easy

Gradable: automatic

Subtopic: Units of Energy

Topic: Thermochemistry

24. Which of the following is not a state function?

A. internal energy

B. volume

C. work

D. pressure

E. enthalpy

Accessibility: Keyboard Navigation

Bloom's: 1. Remember

Difficulty: Easy

Gradable: automatic

Subtopic: First Law of Thermodynamics (Conservation of Energy)

Topic: Thermochemistry

25. Calculate q when 28.6 g of water is heated from 22.0°C to 78.3°C.

A. 0.385 kJ

B. 1.61 kJ

C. 6.74 kJ

D. 9.37 kJ

E. 1.61 × 10³ kJ

Accessibility: Keyboard Navigation

Bloom's: 3. Apply

Difficulty: Easy

Gradable: automatic

Subtopic: Enthalpy (Heats of Reaction)

Topic: Thermochemistry

26. 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).

A. iron

B. copper

C. granite

D. gold

E. water

Accessibility: Keyboard Navigation

Bloom's: 2. Understand

Difficulty: Medium

Gradable: automatic

Subtopic: Enthalpy (Heats of Reaction)

Topic: Thermochemistry

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

A. –1900 kJ

B. –420 kJ

C. –99 kJ

D. –0.42 kJ

E. –4.2 × 10^–6 kJ

Accessibility: Keyboard Navigation

Bloom's: 3. Apply

Difficulty: Easy

Gradable: automatic

Subtopic: Enthalpy (Heats of Reaction)

Topic: Thermochemistry

28. A 275-g sample of nickel at 100.0°C is placed in 100.0 mL of water at 22.0°C. What is the final temperature of the water? Assume that no heat is lost to or gained from the surroundings. Specific heat capacity of nickel = 0.444 J/(g·K)

A. 39.6°C

B. 40.8°C

C. 61.0°C

D. 79.2°C

E. 82.4°C

Accessibility: Keyboard Navigation

Bloom's: 3. Apply

Difficulty: Medium

Gradable: automatic

Subtopic: Enthalpy (Heats of Reaction)

Topic: Thermochemistry

29. 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. –22.7°C

B. 36.7°C

C. 42.7°C

D. 62.7°C

E. None of these choices are correct.

Accessibility: Keyboard Navigation

Bloom's: 3. Apply

Difficulty: Medium

Gradable: automatic

Subtopic: Enthalpy (Heats of Reaction)

Topic: Thermochemistry

30. When Karl Kaveman adds chilled grog to his new granite mug, he removes 10.9 kJ of energy from the mug. If it has a mass of 625 g and was at 25°C, what is its new temperature? Specific heat capacity of granite = 0.79 J/(g·K)

A. 3°C

B. 14°C

C. 22°C

D. 47°C

E. None of these choices are correct.

Accessibility: Keyboard Navigation

Bloom's: 3. Apply

Difficulty: Medium

Gradable: automatic

Subtopic: Enthalpy (Heats of Reaction)

Topic: Thermochemistry

31. The Starship Enterprise is caught in a time warp and Spock is forced to use the primitive techniques of the 20th century to determine the specific heat capacity of an unknown mineral. The 307-g sample was heated to 98.7°C and placed into a calorimeter containing 72.4 g of water at 23.6°C. The heat capacity of the calorimeter was 15.7 J/K. The final temperature in the calorimeter was 32.4°C. What is the specific heat capacity of the mineral?

A. 0.124 J/(g·K)

B. 0.131 J/(g·K)

C. 0.138 J/(g·K)

D. 0.145 J/(g·K)

E. None of these choices are correct.

Accessibility: Keyboard Navigation

Bloom's: 3. Apply

Difficulty: Medium

Gradable: automatic

Subtopic: Enthalpy (Heats of Reaction)

Topic: Thermochemistry

32. A 1.00 g piece of copper metal is initially at 100.0°C. It is dropped into a coffee cup calorimeter containing 50.0 g of water at a temperature of 20.0°C. After stirring, the final temperature of both copper and water is 25.0°C. Assuming no heat losses, and that the specific heat (capacity) of water is 4.18 J/(g·K), what is the heat capacity of the copper in J/K?

A. 2.79 J/(g·K)

B. 3.33 J/(g·K)

C. 13.9 J/(g·K)

D. 209 J/(g·K)

E. None of these choices are correct.

Accessibility: Keyboard Navigation

Bloom's: 3. Apply

Difficulty: Medium

Gradable: automatic

Subtopic: Enthalpy (Heats of Reaction)

Topic: Thermochemistry

33. 15.0 g of ice cubes at 0.0°C are combined with 150. g of liquid water at 70.0°C in a coffee cup calorimeter. Calculate the final temperature reached, assuming no heat loss or gain from the surroundings. (Data: specific heat capacity of H₂O(l), c = 4.18 J/g·°C; H₂O(s) → H₂O(l) ΔH = 6.02 kJ/mol)

A. 0.0

B. 10.6

C. 30.7

D. 43.2

E. 56.4

Accessibility: Keyboard Navigation

Bloom's: 3. Apply

Difficulty: Hard

Gradable: automatic

Subtopic: Enthalpy (Heats of Reaction)

Topic: Thermochemistry

34. 40.0 g of ice cubes at 0.0°C are combined with 150. g of liquid water at 20.0°C in a coffee cup calorimeter. Calculate the final temperature reached, assuming no heat loss or gain from the surroundings. (Data: specific heat capacity of H₂O(l), c = 4.18 J/g·°C; H₂O(s) → H₂O(l) ΔH = 6.02 kJ/mol)

A. 0.0

B. 10.6

C. 30.7

D. 43.2

E. 56.4

Accessibility: Keyboard Navigation

Bloom's: 3. Apply

Difficulty: Hard

Gradable: automatic

Subtopic: Enthalpy (Heats of Reaction)

Topic: Thermochemistry

35. What is the final temperature when 20.0 g of water at 25°C is mixed with 30.0 g of water at 80°C?

A. 35°C

B. 42°C

C. 53°C

D. 58°C

E. 70°C

Accessibility: Keyboard Navigation

Bloom's: 3. Apply

Difficulty: Medium

Gradable: automatic

Subtopic: Enthalpy (Heats of Reaction)

Topic: Thermochemistry

36. 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) ΔH = ΔH_fusion = 6.02 kJ/mol)

A. 1.92 kg

B. 1.90 kg

C. 1.52 kg

D. 855 g

E. < 800 g

Accessibility: Keyboard Navigation

Bloom's: 3. Apply

Difficulty: Hard

Gradable: automatic

Subtopic: Enthalpy (Heats of Reaction)

Topic: Thermochemistry

37. The specific heat capacity c of a metal is approximately related to its molar mass as follows: c × = 3R, where R is the universal gas constant, 8.314 J/mol·K. Use this relationship to identify the metal which has a specific heat capacity of 0.900 J/g·K.

A. Li

B. Sn

C. Ca

D. Al

E. U

Bloom's: 2. Understand

Difficulty: Medium

Gradable: automatic

Subtopic: Enthalpy (Heats of Reaction)

Topic: Thermochemistry

38. The combustion of glucose (C₆H₁₂O₆) with oxygen gas produces carbon dioxide and water. This process releases 2803 kJ per mole of glucose. When 3.00 mol of oxygen react in this way with glucose, what is the energy release in kcal? (Hint: Write a balanced equation for the combustion process.)

A. 223.5 kcal

B. 335.3 kcal

C. 1402 kcal

D. 2012 kcal

E. 5858 kcal

Accessibility: Keyboard Navigation

Bloom's: 3. Apply

Difficulty: Medium

Gradable: automatic

Subtopic: Enthalpy (Heats of Reaction)

Topic: Thermochemistry

39. 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.

A. 670 J

B. 1300 J

C. 27 kJ

D. 54 kJ

E. > 100 kJ

Accessibility: Keyboard Navigation

Bloom's: 3. Apply

Difficulty: Hard

Gradable: automatic

Subtopic: Calorimetry (Measuring Heats of Reaction)

Topic: Thermochemistry

40. 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?

A. –25.0 kJ

B. –7820 kJ

C. –1.56 × 10⁴ kJ

D. –3.13 × 10⁴ kJ

E. None of these choices are correct.

Accessibility: Keyboard Navigation

Bloom's: 3. Apply

Difficulty: Easy

Gradable: automatic

Subtopic: Enthalpy (Heats of Reaction)

Topic: Thermochemistry

41. Calcium hydroxide, which reacts with carbon dioxide to form calcium carbonate, was used by the ancient Romans as mortar in stone structures. The reaction for this process is

Ca(OH)₂(s) + CO₂(g) → CaCO₃(s) + H₂O(g) ΔH = –69.1 kJ

What is the enthalpy change if 3.8 mol of calcium carbonate is formed?

A. –18 kJ

B. –69 kJ

C. –73 kJ

D. –260 kJ

E. None of these choices are correct.

Accessibility: Keyboard Navigation

Bloom's: 3. Apply

Difficulty: Easy

Gradable: automatic

Subtopic: Enthalpy (Heats of Reaction)

Topic: Thermochemistry

42. 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. 203 g

B. 282 g

C. 406 g

D. 478 g

E. 564 g

Accessibility: Keyboard Navigation

Bloom's: 3. Apply

Difficulty: Medium

Gradable: automatic

Subtopic: Enthalpy (Heats of Reaction)

Topic: Thermochemistry

43. 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 = –850 kJ

What mass of iron is formed when 725 kJ of heat are released?

A. 47 g

B. 65 g

C. 95 g

D. 112 g

E. 130 g

Accessibility: Keyboard Navigation

Bloom's: 3. Apply

Difficulty: Medium

Gradable: automatic

Subtopic: Enthalpy (Heats of Reaction)

Topic: Thermochemistry

44. Use Hess's Law to calculate the enthalpy change for the reaction

WO₃(s) + 3H₂(g) → W(s) + 3H₂O(g)

from the following data:

2W(s) + 3O₂(g) → 2WO₃(s) ΔH = –1685.4 kJ

2H₂(g) + O₂(g) → 2H₂O(g) ΔH = –477.84 kJ

A. 125.9 kJ

B. 252.9 kJ

C. 364.9 kJ

D. 1207.6 kJ

E. None of these choices are correct.

Accessibility: Keyboard Navigation

Bloom's: 3. Apply

Difficulty: Medium

Gradable: automatic

Subtopic: Hess's Law

Topic: Thermochemistry

45. Calculate the enthalpy change for the reaction

NO(g) + O(g) → NO₂(g)

from the following data:

NO(g) + O₃(g) → NO₂(g) + O₂(g) ΔH = –198.9 kJ

O₃(g) → 1.5O₂(g) ΔH = –142.3 kJ

O₂(g) → 2O(g) ΔH = 495.0 kJ

A. –551.6 kJ

B. –304.1 kJ

C. 190.9 kJ

D. 153.8 kJ

E. 438.4 kJ

Accessibility: Keyboard Navigation

Bloom's: 3. Apply

Difficulty: Medium

Gradable: automatic

Subtopic: Hess's Law

Topic: Thermochemistry

46. Use the following data to calculate the standard heat (enthalpy) of formation, ΔH_f°, of manganese(IV) oxide, MnO₂ (s).

2MnO₂(s) → 2MnO(s) + O₂(g) ΔH = 264 kJ

MnO₂(s) + Mn(s) → 2MnO(s) ΔH = –240 kJ

A. –504 kJ

B. –372 kJ

C. –24 kJ

D. 24 kJ

E. 504 kJ

Accessibility: Keyboard Navigation

Bloom's: 3. Apply

Difficulty: Medium

Gradable: automatic

Subtopic: Hess's Law

Topic: Thermochemistry

47. 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)

A. 116.8

B. –93.7

C. 227.8

D. –348.3

E. 93.7

Accessibility: Keyboard Navigation

Bloom's: 3. Apply

Difficulty: Medium

Gradable: automatic

Subtopic: Standard Enthalpies of Formation and Reaction (ΔHof, ΔHorxn)

Topic: Thermochemistry

48. 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, ΔH_f°, in kJ/mol. The formation reaction for ammonia is:

0.5N₂(g) + 1.5H₂(g) → NH₃(g).

A. –46 kJ/mol

B. –13.5 kJ/mol

C. –3.97 kJ/mol

D. 3.97 kJ/mol

E. 13.5 kJ/mol

Accessibility: Keyboard Navigation

Bloom's: 3. Apply

Difficulty: Hard

Gradable: automatic

Subtopic: Enthalpy (Heats of Reaction)

Topic: Thermochemistry

49. Which one of the following statements about standard states is incorrect?

A. The standard state of a solid compound is the pure solid.

B. The standard state of a liquid compound is the pure liquid.

C. The standard state of a gaseous compound is the gas at a pressure of 1 atmosphere.

D. The standard state of an aqueous solute is a saturated solution in water.

E. The standard state of an element is the form in which it is stable at 1 atm and a specified temperature, usually 25°C.

Accessibility: Keyboard Navigation

Bloom's: 1. Remember

Difficulty: Easy

Gradable: automatic

Subtopic: Standard Enthalpies of Formation and Reaction (ΔHof, ΔHorxn)

Topic: Thermochemistry

50. Which one of the following equations represents the formation reaction of CH₃OH(l)?

A. C(g) + 2H₂(g) + ½O₂(g) → CH₃OH(l)

B. C(g) + 4H(g) + O(g) → CH₃OH(l)

C. C(graphite) + 4H(g) + O(g) → CH₃OH(l)

D. C(diamond) + 4H(g) + O(g) → CH₃OH(l)

E. C(graphite) + 2H₂(g) + ½O₂(g) → CH₃OH(l)

Accessibility: Keyboard Navigation

Bloom's: 2. Understand

Difficulty: Easy

Gradable: automatic

Subtopic: Standard Enthalpies of Formation and Reaction (ΔHof, ΔHorxn)

Topic: Thermochemistry

51. Which one of the following is not a correct formation reaction? (products are correct)

A. H₂(g) + O(g) → H₂O(l)

B. ½H₂(g) + ½Cl₂(g) → HCl(g)

C. 6C(graphite) + 3H₂(g) → C₆H₆(l)

D. C(graphite) → C(diamond)

E. 6C(graphite) + 6H₂(g) + 3O₂(g) → C₆H₁₂O₆(s)

Accessibility: Keyboard Navigation

Bloom's: 2. Understand

Difficulty: Easy

Gradable: automatic

Subtopic: Standard Enthalpies of Formation and Reaction (ΔHof, ΔHorxn)

Topic: Thermochemistry

52. Which one of the following is a correct formation reaction?

A. C(diamond) → C(graphite)

B. H₂(g) + O(g) → H₂O(l)

C. C(graphite) + 4H(g) → CH₄(g)

D. 6C(graphite) + 6H₂O(s) → C₆H₁₂O₆(s)

E. 2C(graphite) + 3H₂(g) + ½O₂(g) → C₂H₅OH(l)

Accessibility: Keyboard Navigation

Bloom's: 2. Understand

Difficulty: Easy

Gradable: automatic

Subtopic: Standard Enthalpies of Formation and Reaction (ΔHof, ΔHorxn)

Topic: Thermochemistry

53. Calculate the ΔH°_rxn for the decomposition of calcium carbonate to calcium oxide and carbon dioxide.

ΔH°_f [CaCO₃(s)] = –1206.9 kJ/mol; ΔH°_f [CaO(s)] = –635.1 kJ/mol;

ΔH°_f [CO₂(g)] = –393.5 kJ/mol

CaCO₃(s) → CaO(s) + CO₂(g)

A. –2235.5 kJ

B. –1448.5 kJ

C. –178.3 kJ

D. 178.3 kJ

E. 2235.5 kJ

Accessibility: Keyboard Navigation

Bloom's: 3. Apply

Difficulty: Easy

Gradable: automatic

Subtopic: Standard Enthalpies of Formation and Reaction (ΔHof, ΔHorxn)

Topic: Thermochemistry

54. Nitric acid, which is among the top 15 chemicals produced in the United States, was first prepared over 1200 years ago by heating naturally occurring sodium nitrate (called saltpeter) with sulfuric acid and collecting the vapors produced. Calculate ΔH°_rxn for this reaction. ΔH°_f [NaNO₃(s)] = –467.8 kJ/mol; ΔH°_f [NaHSO₄(s)] = –1125.5 kJ/mol;

ΔH°_f [H₂SO₄(l) = –814.0 kJ/mol; ΔH°_f [HNO₃(g)] = –135.1 kJ/mol

NaNO₃(s) + H₂SO₄(l) → NaHSO₄(s) + HNO₃(g)

A. –644.2 kJ

B. –291.4 kJ

C. –21.2 kJ

D. 21.2 kJ

E. 644.2 kJ

Accessibility: Keyboard Navigation

Bloom's: 3. Apply

Difficulty: Easy

Gradable: automatic

Subtopic: Standard Enthalpies of Formation and Reaction (ΔHof, ΔHorxn)

Topic: Thermochemistry

55. 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

A. –906.0 kJ

B. –197.4 kJ

C. –105.6 kJ

D. 197.4 kJ

E. 906.0 kJ

Accessibility: Keyboard Navigation

Bloom's: 3. Apply

Difficulty: Easy

Gradable: automatic

Subtopic: Standard Enthalpies of Formation and Reaction (ΔHof, ΔHorxn)

Topic: Thermochemistry

56. Calculate the ΔH°_rxn for the following reaction. (ΔH°_f [SiO₂(s)] = –910.9 kJ/mol;

ΔH°_f [SiCl₄(g)] = –657.0 kJ/mol; ΔH°_f [HCl(g)] = –92.3 kJ/mol; ΔH°_f [H₂O(g)] = –241.8 kJ/mol)

SiO₂(s) + 4HCl(g) → SiCl₄(g) + 2H₂O(g)

A. –139.5 kJ

B. –137.4 kJ

C. –104.4 kJ

D. 104.4 kJ

E. 139.5 kJ

Accessibility: Keyboard Navigation

Bloom's: 3. Apply

Difficulty: Easy

Gradable: automatic

Subtopic: Standard Enthalpies of Formation and Reaction (ΔHof, ΔHorxn)

Topic: Thermochemistry

57. 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)

A. –1981.4 kJ

B. –685.2 kJ

C. –172.2 kJ

D. 172.2 kJ

E. 685.2 kJ

Accessibility: Keyboard Navigation

Bloom's: 3. Apply

Difficulty: Easy

Gradable: automatic

Subtopic: Standard Enthalpies of Formation and Reaction (ΔHof, ΔHorxn)

Topic: Thermochemistry

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

(ΔH°_f [C₂H₅OH(l)] = –277.7 kJ/mol; ΔH°_f [CO₂(g)] = –393.5 kJ/mol; ΔH°_f [H2O(g)] = –241.8 kJ/mol)

A. –1234.7 kJ

B. –751.1 kJ

C. –357.6 kJ

D. 357.6 kJ

E. 1234.7 kJ

Accessibility: Keyboard Navigation

Bloom's: 3. Apply

Difficulty: Medium

Gradable: automatic

Subtopic: Standard Enthalpies of Formation and Reaction (ΔHof, ΔHorxn)

Topic: Thermochemistry

59. In a reaction with high energy reactants and low energy products, q is negative.

Accessibility: Keyboard Navigation

Bloom's: 2. Understand

Difficulty: Medium

Gradable: automatic

Subtopic: Enthalpy (Heats of Reaction)

Topic: Thermochemistry

60. The only way in which a system can do work on the surroundings is by expansion against the external pressure.

Accessibility: Keyboard Navigation

Bloom's: 1. Remember

Difficulty: Medium

Gradable: automatic

Subtopic: System/Surroundings and Heat/Work

Topic: Thermochemistry

61. For all processes, both q and w will have the same sign.

Accessibility: Keyboard Navigation

Bloom's: 1. Remember

Difficulty: Easy

Gradable: automatic

Subtopic: System/Surroundings and Heat/Work

Topic: Thermochemistry

62. For all processes, both q and ΔE will have the same sign.

Accessibility: Keyboard Navigation

Bloom's: 2. Understand

Difficulty: Easy

Gradable: automatic

Subtopic: First Law of Thermodynamics (Conservation of Energy)

Topic: Thermochemistry

63. For a reaction in a sealed, rigid container, ΔH is always greater than ΔE.

Accessibility: Keyboard Navigation

Bloom's: 2. Understand

Difficulty: Medium

Gradable: automatic

Subtopic: First Law of Thermodynamics (Conservation of Energy)

Topic: Thermochemistry

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

Accessibility: Keyboard Navigation

Bloom's: 2. Understand

Difficulty: Easy

Gradable: automatic

Subtopic: First Law of Thermodynamics (Conservation of Energy)

Topic: Thermochemistry

65. The enthalpy (H) of liquid water is greater than that of the same quantity of ice at the same temperature.

Accessibility: Keyboard Navigation

Bloom's: 2. Understand

Difficulty: Easy

Gradable: automatic

Subtopic: Enthalpy (Heats of Reaction)

Topic: Thermochemistry

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

Accessibility: Keyboard Navigation

Bloom's: 1. Remember

Difficulty: Easy

Gradable: automatic

Subtopic: Enthalpy (Heats of Reaction)

Topic: Thermochemistry

67. ΔE values obtained by bomb calorimetry can be converted to give accurate ΔH values.

Accessibility: Keyboard Navigation

Bloom's: 1. Remember

Difficulty: Medium

Gradable: automatic

Subtopic: Calorimetry (Measuring Heats of Reaction)

Topic: Thermochemistry

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

Accessibility: Keyboard Navigation

Bloom's: 1. Remember

Difficulty: Easy

Gradable: automatic

Subtopic: Standard Enthalpies of Formation and Reaction (ΔHof, ΔHorxn)

Topic: Thermochemistry

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

Accessibility: Keyboard Navigation

Bloom's: 2. Understand

Difficulty: Easy

Gradable: automatic

Subtopic: Standard Enthalpies of Formation and Reaction (ΔHof, ΔHorxn)

Topic: Thermochemistry

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

Accessibility: Keyboard Navigation

Bloom's: 2. Understand

Difficulty: Medium

Gradable: automatic

Subtopic: Standard Enthalpies of Formation and Reaction (ΔHof, ΔHorxn)

Topic: Thermochemistry

71. Combustion of a hydrocarbon will release more energy than combustion of an equal mass of carbohydrate because

A. the C-O and O-H single bonds in carbohydrates are weak.

B. carbohydrates contain C-O and O-H bonds and hydrocarbons do not.

C. the total energy of the C-C and C-H bonds in hydrocarbons is greater than the total energy of the C=O and O-H bonds in the combustion products (carbon dioxide and water).

D. the total energy of the bonds in hydrocarbons is greater than the energy of the bonds in carbohydrates.

E. hydrocarbons have higher molar masses than carbohydrates.

Accessibility: Keyboard Navigation

Bloom's: 2. Understand

Difficulty: Medium

Gradable: automatic

Subtopic: Calorimetry (Measuring Heats of Reaction)

Topic: Thermochemistry

72. In which one of the following processes is ΔH = ΔE?

A. 2HI(g) → H₂(g) + I₂(g) at atmospheric pressure.

B. Two moles of ammonia gas are cooled from 325 °C to 300 °C at 1.2 atm.

C. H₂O(l) → H₂O(g) at 100 °C at atmospheric pressure.

D. CaCO₃(s) → CaO(s) + CO₂(g) at 800 °C at atmospheric pressure.

E. CO₂(s) → CO₂(g) at atmospheric pressure.

Accessibility: Keyboard Navigation

Bloom's: 2. Understand

Difficulty: Medium

Gradable: automatic

Subtopic: Enthalpy (Heats of Reaction)

Topic: Thermochemistry

Category # of Questions

Accessibility: Keyboard Navigation 71

Bloom's: 1. Remember 8

Bloom's: 2. Understand 25

Bloom's: 3. Apply 39

Difficulty: Easy 33

Difficulty: Hard 7

Difficulty: Medium 32

Gradable: automatic 72

Subtopic: Calorimetry (Measuring Heats of Reaction) 3

Subtopic: Enthalpy (Heats of Reaction) 27

Subtopic: First Law of Thermodynamics (Conservation of Energy) 13

Subtopic: Hess's Law 3

Subtopic: Standard Enthalpies of Formation and Reaction (ΔHof, ΔHorxn) 14

Subtopic: System/Surroundings and Heat/Work 9

Subtopic: Units of Energy 3

Topic: Thermochemistry 72