- The energy associated with the separation of two electrical charges is called _____.
| A) | heat |
| B) | internal energy |
| C) | temperature |
| D) | kinetic energy |
| E) | potential energy |
ANS: E PTS: 1 DIF: easy REF: 6.1
OBJ: Define energy, kinetic energy, potential energy, and internal energy.
TOP: thermochemistry | heats of reaction
- The energy associated with the motion of a speeding bullet is called _____.
| A) | heat |
| B) | internal energy |
| C) | temperature |
| D) | kinetic energy |
| E) | potential energy |
ANS: D PTS: 1 DIF: easy REF: 6.1
OBJ: Define energy, kinetic energy, potential energy, and internal energy.
TOP: thermochemistry | heats of reaction
- The air whipped up by a tornado possesses what type(s) of energy?
| A) | potential energy only |
| B) | internal energy only |
| C) | kinetic energy only |
| D) | kinetic energy, potential energy, and internal energy |
| E) | kinetic energy and potential energy only |
ANS: D PTS: 1 DIF: easy REF: 6.1
OBJ: Define energy, kinetic energy, potential energy, and internal energy.
TOP: thermochemistry | heats of reaction
- The internal energy of a substance is defined as
| A) | the potential energy of all particles which make up the substance. |
| B) | the kinetic energy of all particles which make up the substance. |
| C) | the sum of the potential and kinetic energy of all particles which make up the substance. |
| D) | the thermal energy of all particles which make up the substance. |
| E) | the chemical energy of all particles which make up the substance. |
ANS: C PTS: 1 DIF: easy REF: 6.1
OBJ: Define energy, kinetic energy, potential energy, and internal energy.
TOP: thermochemistry | heats of reaction
- What is the kinetic energy of a 2000-lb car traveling at 48 miles per hour? (1 lb = 0.4536 kg, 1 mi = 1.609 km)
| A) | 2.1 ´ 10–7 J |
| B) | 1.0 ´ 106 J |
| C) | 3.5 ´ 1019 J |
| D) | 2.1 ´ 105 J |
| E) | 3.1 ´ 10–8 J |
ANS: D PTS: 1 DIF: easy REF: 6.1
OBJ: Calculate the kinetic energy of a moving object. (Example 6.1)
TOP: thermochemistry | heats of reaction KEY: energy | kinetic energy
MSC: general chemistry
- Calculate DU of a gas for a process in which the gas absorbs 9 J of heat and does 25 J of work by expanding.
| A) | 16 J |
| B) | 34 J |
| C) | –34 J |
| D) | 0, because DU is a state function |
| E) | –16 J |
ANS: E PTS: 1 DIF: easy REF: 6.2
OBJ: State the law of conservation of energy.
TOP: thermochemistry | heats of reaction KEY: energy | law of conservation of energy
MSC: general chemistry
- Which of the following is an endothermic process?
| A) | work is done by the system on the surroundings |
| B) | heat energy flows from the system to the surroundings |
| C) | work is done on the system by the surroundings |
| D) | heat energy is evolved by the system |
| E) | none of the above |
ANS: C PTS: 1 DIF: moderate REF: 6.3
OBJ: Distinguish between an exothermic process and an endothermic process.
TOP: thermochemistry | heats of reaction
- Which of the following does not result in a change in the internal energy of the system?
| A) | work is done on the system |
| B) | work is done on the surroundings |
| C) | heat flows into the system |
| D) | heat flows to the surroundings |
| E) | none of the above |
ANS: E PTS: 1 DIF: easy REF: 6.2
OBJ: Define work and heat. | Define the change in internal energy of a system.
TOP: thermochemistry | heats of reaction
- Which of the following statements about heat is false?
| A) | If heat flows into a system, the extra energy of the system appears in the form of internal energy. |
| B) | A hot object possesses more heat than a cold object. |
| C) | If the system and surroundings are in thermal equilibrium, there is no heat flow between them. |
| D) | A process in which heat flows out of a system is said to be exothermic. |
| E) | Heat is a form of energy flow. |
ANS: B PTS: 1 DIF: easy REF: 6.2
OBJ: Define heat and heat of reaction. TOP: thermochemistry | heats of reaction
KEY: heat MSC: general chemistry
- If q = –91 kJ for a certain process, that process
| A) | requires a catalyst. |
| B) | is exothermic. |
| C) | occurs rapidly. |
| D) | is endothermic. |
| E) | cannot occur. |
ANS: B PTS: 1 DIF: easy REF: 6.3
OBJ: Distinguish between an exothermic process and an endothermic process.
TOP: thermochemistry | heats of reaction KEY: heat | heat of reaction
MSC: general chemistry
- If q = 28 kJ and w = 85 kJ for a certain process, that process
| A) | requires a catalyst. |
| B) | is endothermic. |
| C) | occurs slowly. |
| D) | is exothermic. |
| E) | cannot occur. |
ANS: B PTS: 1 DIF: easy to moderate
REF: 6.3
OBJ: Distinguish between an exothermic process and an endothermic process.
TOP: thermochemistry | heats of reaction
- What is the change in internal energy of the system (DU) if 10 kJ of heat energy is absorbed by the system and 70 kJ of work is done by the system for a certain process?
| A) | –60 kJ |
| B) | 80 kJ |
| C) | 10 kJ |
| D) | 60 kJ |
| E) | –80 kJ |
ANS: A PTS: 1 DIF: moderate REF: 6.2
OBJ: Express the first law of thermodynamics mathematically.
TOP: thermochemistry | heats of reaction
- At constant pressure, the sign of q for the process CO2(s) ® CO2(g) is expected to be
| A) | positive, and the process is exothermic. |
| B) | negative, and the process is exothermic. |
| C) | impossible to predict. |
| D) | positive, and the process is endothermic. |
| E) | negative, and the process is endothermic. |
ANS: D PTS: 1 DIF: easy REF: 6.3
OBJ: Distinguish between an exothermic process and an endothermic process.
TOP: thermochemistry | heats of reaction KEY: heat | heat of reaction
MSC: general chemistry
- At constant pressure, the sign of q for the process H2O(l) ® H2O(s) is expected to be
| A) | positive, and the process is exothermic. |
| B) | negative, and the process is endothermic. |
| C) | impossible to predict. |
| D) | negative, and the process is exothermic. |
| E) | positive, and the process is endothermic. |
ANS: D PTS: 1 DIF: easy REF: 6.2
OBJ: Distinguish between an exothermic process and an endothermic process.
TOP: thermochemistry | heats of reaction KEY: heat | heat of reaction
MSC: general chemistry
- Which of the following statements is not true for an exothermic reaction?
| A) | The products have a higher heat content than the reactants. |
| B) | The temperature of the reaction system increases. |
| C) | The temperature of the surroundings increases. |
| D) | Heat passes from the reaction system to the surroundings. |
| E) | The enthalpy change for the reaction is negative. |
ANS: A PTS: 1 DIF: easy REF: 6.2
OBJ: Distinguish between an exothermic process and an endothermic process.
TOP: thermochemistry | heats of reaction KEY: enthalpy | enthalpy change
MSC: general chemistry
- H2 and F2 react according to the following equation, forming HF.
H2(g) + F2(g) ® 2HF(g); DH° = –271 kJ
If H2(g) and F2(g) were mixed in a thermally insulated vessel, the reaction that occurred would be
| A) | endothermic, and the temperature of the reaction system would fall. |
| B) | We could not tell unless the original and final temperatures were given. |
| C) | exothermic, and the temperature of the reaction system would fall. |
| D) | exothermic, and the temperature of the reaction system would rise. |
| E) | endothermic, and the temperature of the reaction system would rise. |
ANS: D PTS: 1 DIF: easy REF: 6.3
OBJ: Distinguish between an exothermic process and an endothermic process.
TOP: thermochemistry | heats of reaction KEY: enthalpy | enthalpy of reaction
MSC: general chemistry
- Which of the following statements is incorrect?
| A) | Internal energy is a state function. |
| B) | The value of q is positive when heat flows into a system from the surroundings. |
| C) | The value of q is positive in an endothermic process. |
| D) | Heat flows from a system into the surroundings in an endothermic process. |
| E) | Enthalpy is a state function. |
ANS: D PTS: 1 DIF: easy REF: 6.2
OBJ: Distinguish between an exothermic process and an endothermic process.
TOP: thermochemistry | heats of reaction KEY: heat MSC: general chemistry
- Which of the following statements about enthalpy is false?
| A) | Enthalpy is a state function. |
| B) | At constant pressure, the enthalpy change is equal to the heat absorbed or released. |
| C) | Enthalpy is an extensive property. |
| D) | The change in enthalpy of a process cannot be negative. |
| E) | The SI unit of enthalpy is J. |
ANS: D PTS: 1 DIF: easy REF: 6.3
OBJ: Define enthalpy and enthalpy of reaction.
TOP: thermochemistry | heats of reaction KEY: enthalpy MSC: general chemistry
- The phrase “the heat absorbed or released by a system undergoing a physical or chemical change at constant pressure” is
| A) | the change in enthalpy of the system. |
| B) | the change in internal energy of the system. |
| C) | the definition of a state function. |
| D) | the temperature change of the system. |
| E) | a statement of Hess’s law. |
ANS: A PTS: 1 DIF: easy REF: 6.3
OBJ: Explain how the terms enthalpy of reaction and heat of reaction are related.
TOP: thermochemistry | heats of reaction KEY: enthalpy | enthalpy change
MSC: general chemistry
- Which of the following statements is true concerning the decomposition of liquid water to form hydrogen gas and oxygen gas?
2H2O(l) ® 2H2(g) + O2(g)
| A) | DH is greater than DU because the pressure is constant. |
| B) | DH is less than DU because of the pressure–volume work done by the gaseous products. |
| C) | DH is less than DU because the atmosphere does pressure–volume work on the gaseous products. |
| D) | DH equals DU because both are state functions. |
| E) | DH is greater than DU because of the pressure–volume work done by the gaseous products. |
ANS: E PTS: 1 DIF: moderate REF: 6.3
OBJ: Explain how enthalpy and internal energy are related.
TOP: thermochemistry | heats of reaction KEY: enthalpy | enthalpy and internal energy
MSC: general chemistry
- Under conditions of constant pressure, for which of the following reactions is the magnitude of pressure-volume work going to be greatest?
| A) | BaO(s) + SO3(g) ® BaSO4(s) |
| B) | 2NO(g) + O2(g) ® 2NO2(g) |
| C) | 2H2O2(l) ® 2H2O(l) + O2(g) |
| D) | 2KClO3(s) ® 2KCl(s) + 3O2(g) |
| E) | H2(g) + Cl2(g) ® 2HCl(g) |
ANS: D PTS: 1 DIF: moderate REF: 6.3
OBJ: Describe pressure-volume work verbally and mathematically.
TOP: thermochemistry | heats of reaction
- Under conditions of constant pressure, for which of the following reactions is the magnitude of pressure-volume work going to be smallest?
| A) | BaO(s) + SO3(g) ® BaSO4(s) |
| B) | 2NO(g) + O2(g) ® 2NO2(g) |
| C) | 2H2O2(l) ® 2H2O(l) + O2(g) |
| D) | 2KClO3(s) ® 2KCl(s) + 3O2(g) |
| E) | H2(g) + Cl2(g) ® 2HCl(g) |
ANS: E PTS: 1 DIF: moderate REF: 6.3
OBJ: Describe pressure-volume work verbally and mathematically.
TOP: thermochemistry | heats of reaction
- Which of the following sentences accurately describes the thermochemical equation given below?
2Ag(s) + F2(g) ® 2AgF(s); DH = –409.2 kJ
| A) | If 2 mol of silver metal react with 1 mol of fluorine gas at constant volume, 2 mol of solid sodium fluoride is produced and 409.2 kJ of heat is consumed. |
| B) | If 2 atoms of silver metal react with 1 molecule of fluorine gas at constant pressure, 2 formula units of solid sodium fluoride are produced and 409.2 kJ of heat is released. |
| C) | If 2 atoms of silver metal react with 1 molecule of fluorine gas at constant pressure, 2 formula units of solid sodium fluoride are produced and 409.2 kJ of heat is consumed. |
| D) | If 2 mol of silver metal react with 1 mol of fluorine gas at constant pressure, 2 mol of solid sodium fluoride is produced and 409.2 kJ of heat is consumed. |
| E) | If 2 mol of silver metal react with 1 mol of fluorine gas at constant pressure, 2 mol of solid sodium fluoride is produced and 409.2 kJ of heat is released. |
ANS: E PTS: 1 DIF: easy REF: 6.4
OBJ: Write a thermochemical equation given pertinent information. (Example 6.2)
TOP: thermochemistry | heats of reaction KEY: thermochemical equation
MSC: general chemistry
- Which of the following statements is incorrect concerning the thermochemical equation below?
2SO3(g) ® 2SO2(g) + O2(g); DH° = 198 kJ
| A) | The enthalpy of the reactants exceeds that of the products. |
| B) | The reaction is endothermic. |
| C) | For the reaction 2SO2(g) + O2(g) ® 2SO3(g), DH° = –198 kJ. |
| D) | The external pressure is 1 atm. |
| E) | For every mole of SO3(g) consumed, 99 kJ of heat at constant pressure is consumed as well. |
ANS: A PTS: 1 DIF: easy REF: 6.4
OBJ: Write a thermochemical equation given pertinent information. (Example 6.2)
TOP: thermochemistry | heats of reaction KEY: thermochemical equation
MSC: general chemistry
- In a certain experiment, 0.1000 mol of hydrogen gas reacted with 0.1000 mol of solid iodine at a constant 1 atm pressure, producing 0.2000 mol of solid hydrogen iodide and absorbing 5.272 kJ of heat in the process. Which of the following thermochemical equations correctly describes this experiment?
| A) | H2(g) + I2(s) ® 2HI(s); DH° = –52.72 kJ |
| B) | H2(g) + I2(s) ® 2HI(s); DH° = 5.272 kJ |
| C) | H2(g) + I2(s) ® 2HI(s); DH° = –5.272 kJ |
| D) | H2(g) + I2(s) ® 2HI(s); DH° = 10.54 kJ |
| E) | H2(g) + I2(s) ® 2HI(s); DH° = 52.72 kJ |
ANS: E PTS: 1 DIF: difficult REF: 6.4
OBJ: Write a thermochemical equation given pertinent information. (Example 6.2)
TOP: thermochemistry | heats of reaction KEY: thermochemical equation
MSC: general chemistry
- Given:
4AlCl3(s) + 3O2(g) ® 2Al2O3(s) + 6Cl2(g); DH = –529.0 kJ
determine DH for the following thermochemical equation.
Cl2(g) + Al2O3(s) ® AlCl3(s) + O2(g)
| A) | +264.5 kJ |
| B) | +529.0 kJ |
| C) | +88.2 kJ |
| D) | +176.3 kJ |
| E) | –176.3 kJ |
ANS: C PTS: 1 DIF: easy REF: 6.4
OBJ: Manipulate a thermochemical equation using these rules. (Example 6.3)
TOP: thermochemistry | heats of reaction KEY: thermochemical equation
MSC: general chemistry
- Given the thermochemical equation
2Al(s) + O2(g) ® Al2O3(s); DH = –1676 kJ
find DH for the following reaction.
2Al2O3(s) ® 4Al(s) + 3O2(g)
| A) | 838 kJ |
| B) | 1676 kJ |
| C) | –1676 kJ |
| D) | 3352 kJ |
| E) | –838 kJ |
ANS: D PTS: 1 DIF: easy REF: 6.4
OBJ: Manipulate a thermochemical equation using these rules. (Example 6.3)
TOP: thermochemistry | heats of reaction
KEY: thermochemical equation | enthalpy of reaction MSC: general chemistry
- Given:
what is DH for the following thermochemical equation?
| A) | 986.9 kJ |
| B) | -986.9 kJ |
| C) | –139 MJ |
| D) | –2320 kJ |
| E) | –38.7 kJ |
ANS: A PTS: 1 DIF: easy REF: 6.4
OBJ: Manipulate a thermochemical equation using these rules. (Example 6.3)
TOP: thermochemistry | heats of reaction
- Which of the following statements is false concerning the reaction of hydrogen gas and oxygen gas given below?
H2(g) + O2(g) ® H2O(l); DH = –285.8 kJ
| A) | Per mole of O2, the change in enthalpy is –571.6 kJ. |
| B) | The value –571.6 kJ pertains to 1 mol of liquid water. |
| C) | If the equation is reversed, DH becomes +285.8 kJ. |
| D) | If the equation is multiplied by 2, DH becomes –571.6 kJ. |
| E) | For the reaction H2(g) + O2(g) ® H2O(g), DH is not equal to –285.8 kJ. |
ANS: B PTS: 1 DIF: moderate REF: 6.4
OBJ: Manipulate a thermochemical equation using these rules. (Example 6.3)
TOP: thermochemistry | heats of reaction KEY: thermochemical equation
MSC: general chemistry
- What is the change in enthalpy when 4.00 mol of sulfur trioxide decomposes to sulfur dioxide and oxygen gas?
2SO2(g) + O2(g) ® 2SO3(g); DH° = 198 kJ
| A) | 396 kJ |
| B) | –198 kJ |
| C) | –396 kJ |
| D) | 198 kJ |
| E) | 792 kJ |
ANS: C PTS: 1 DIF: easy REF: 6.5
OBJ: Calculate the heat absorbed or evolved from a reaction given its enthalpy of reaction and the mass of a reactant or product. (Example 6.4)
TOP: thermochemistry | heats of reaction
KEY: thermochemical equation | stoichiometry and heats of reaction
MSC: general chemistry
- What is the change in enthalpy at 25°C and 1 atm for the production of 9.00 mol SnO(s)?
Sn(s) + SnO2(s) ® 2SnO(s); DH° = 16.2 kJ
| A) | –72.9 kJ |
| B) | –16.2 kJ |
| C) | 16.2 kJ |
| D) | 1.80 kJ |
| E) | 72.9 kJ |
ANS: E PTS: 1 DIF: easy REF: 6.5
OBJ: Calculate the heat absorbed or evolved from a reaction given its enthalpy of reaction and the mass of a reactant or product. (Example 6.4)
TOP: thermochemistry | heats of reaction
KEY: thermochemical equation | stoichiometry and heats of reaction
MSC: general chemistry
- What is the change in enthalpy at 25°C and 1 atm for the reaction of 5.00 mol of elemental iron with excess oxygen gas?
4Fe(s) + 3O2(g) ® 2Fe2O3(s); DH° = –1651 kJ
| A) | -1651 kJ |
| B) | 2752 kJ |
| C) | 2064 kJ |
| D) | –2064 kJ |
| E) | -412.8 kJ |
ANS: D PTS: 1 DIF: easy REF: 6.5
OBJ: Calculate the heat absorbed or evolved from a reaction given its enthalpy of reaction and the mass of a reactant or product. (Example 6.4)
TOP: thermochemistry | heats of reaction
- What is the quantity of heat evolved at constant pressure when 60.3 g H2O(l) is formed from the combustion of H2(g) and O2(g)?
H2(g) + O2(g) ® H2O(l); DH° = –285.8 kJ
| A) | 1.17 ´ 10–2 kJ |
| B) | 285.8 kJ |
| C) | 1.72 ´ 104 kJ |
| D) | 85.4 kJ |
| E) | 9.57 ´ 102 kJ |
ANS: E PTS: 1 DIF: easy REF: 6.5
OBJ: Calculate the heat absorbed or evolved from a reaction given its enthalpy of reaction and the mass of a reactant or product. (Example 6.4)
TOP: thermochemistry | heats of reaction
KEY: thermochemical equation | stoichiometry and heats of reaction
MSC: general chemistry
- What quantity, in moles, of hydrogen is consumed when 676.8 kJ of energy is evolved from the combustion of a mixture of H2(g) and O2(g)?
H2(g) + O2(g) ® H2O(l); DH° = –285.8 kJ
| A) | 2.368 mol |
| B) | 1.184 mol |
| C) | 0.4223 mol |
| D) | 3.368 mol |
| E) | 1.368 mol |
ANS: A PTS: 1 DIF: easy REF: 6.5
OBJ: Calculate the heat absorbed or evolved from a reaction given its enthalpy of reaction and the mass of a reactant or product. (Example 6.4)
TOP: thermochemistry | heats of reaction
- What mass of hydrogen is consumed when 587.9 kJ of energy is evolved from the combustion of a mixture of H2(g) and O2(g)?
H2(g) + O2(g) ® H2O(l); DH° = –285.8 kJ
| A) | 4.147 g |
| B) | 2.073 g |
| C) | 0.2412 g |
| D) | 6.162 g |
| E) | 2.131 g |
ANS: A PTS: 1 DIF: easy REF: 6.5
OBJ: Calculate the heat absorbed or evolved from a reaction given its enthalpy of reaction and the mass of a reactant or product. (Example 6.4)
TOP: thermochemistry | heats of reaction
- According to the following thermochemical equation, if 951.1 g of NO2 is produced, how much heat is released at constant pressure?
2NO(g) + O2(g) ® 2NO2(g); DH° = –114.4 kJ
| A) | 114.4 kJ |
| B) | 1.183 ´ 103 kJ |
| C) | 2.365 ´ 103 kJ |
| D) | 5.534 kJ |
| E) | 1.088 ´ 105 kJ |
ANS: B PTS: 1 DIF: easy REF: 6.5
OBJ: Calculate the heat absorbed or evolved from a reaction given its enthalpy of reaction and the mass of a reactant or product. (Example 6.4)
TOP: thermochemistry | heats of reaction
KEY: thermochemical equation | stoichiometry and heats of reaction
MSC: general chemistry
- Consider the following thermochemical equation:
N2(g) + 2O2(g) ® 2NO2(g); DH° = 66.2 kJ
From this equation, we may conclude that 66.2 kJ is the quantity of heat that is
| A) | gained from the surroundings when 1 mol of NO2 is formed at constant pressure. |
| B) | lost to the surroundings when 1 mol of NO2 is formed at constant pressure. |
| C) | gained from the surroundings when 2 mol of NO2 is formed at constant pressure. |
| D) | lost to the surroundings when 2 mol of NO2 is formed at constant pressure. |
| E) | lost to the surroundings when 1 mol of O2 is consumed at constant pressure. |
ANS: C PTS: 1 DIF: easy REF: 6.5
OBJ: Calculate the heat absorbed or evolved from a reaction given its enthalpy of reaction and the mass of a reactant or product. (Example 6.4)
TOP: thermochemistry | heats of reaction
KEY: thermochemical equation | stoichiometry and heats of reaction
MSC: general chemistry
- How much heat is liberated at constant pressure if 0.834 g of calcium carbonate reacts with 48.9 mL of 0.668 M hydrochloric acid?
CaCO3(s) + 2HCl(aq) ® CaCl2(aq) + H2O(l) + CO2(g); DH° = –15.2 kJ
| A) | –0.127 kJ |
| B) | –0.375 kJ |
| C) | –12.7 kJ |
| D) | –0.248 kJ |
| E) | –10.2 kJ |
ANS: A PTS: 1 DIF: moderate REF: 6.5
OBJ: Calculate the heat absorbed or evolved from a reaction given its enthalpy of reaction and the mass of a reactant or product. (Example 6.4)
TOP: thermochemistry | heats of reaction
KEY: thermochemical equation | stoichiometry and heats of reaction
MSC: general chemistry
- When 34.1 g of lead reacts with 6.81 L of oxygen gas, measured at 1.00 atm and 25.0°C, 36.1 kJ of heat is released at constant pressure. What is DH° for this reaction? (R = 0.0821 L • atm/(K • mol))
2Pb(s) + O2(g) ® 2PbO(s)
| A) | –4.39 ´ 102 kJ |
| B) | –5.94 ´ 101 kJ |
| C) | –3.61 ´ 101 kJ |
| D) | –2.19 ´ 102 kJ |
| E) | –1.30 ´ 102 kJ |
ANS: A PTS: 1 DIF: moderate REF: 6.5
OBJ: Calculate the heat absorbed or evolved from a reaction given its enthalpy of reaction and the mass of a reactant or product. (Example 6.4)
TOP: thermochemistry | heats of reaction
KEY: thermochemical equation | stoichiometry and heats of reaction
MSC: general chemistry
- How much heat is evolved upon the complete oxidation of 9.118 g of aluminum at 25°C and 1 atm pressure? ( for Al2O3 is –1676 kJ/mol.)
4Al(s) + 3O2(g) ® 2Al2O3(s)
| A) | 1.528 ´ 104 kJ |
| B) | 566.4 kJ |
| C) | 1133 kJ |
| D) | 283.2 kJ |
| E) | 141.6 kJ |
ANS: D PTS: 1 DIF: moderate REF: 6.5
OBJ: Calculate the heat absorbed or evolved from a reaction given its enthalpy of reaction and the mass of a reactant or product. (Example 6.4)
TOP: thermochemistry | heats of reaction
KEY: thermochemical equation | stoichiometry and heats of reaction
MSC: general chemistry
- The reaction of iron with hydrochloric acid is represented by the following thermochemical equation.
Fe(s) + 2HCl(aq) ® FeCl2(aq) + H2(g); DH° = –87.9 kJ
How much heat is liberated at constant pressure if 0.358 g of iron reacts with 34.1 mL of 0.588 M HCl?
| A) | 4.09 kJ |
| B) | 31.5 kJ |
| C) | 0.563 kJ |
| D) | 0.881 kJ |
| E) | 87.9 kJ |
ANS: C PTS: 1 DIF: moderate REF: 6.5
OBJ: Calculate the heat absorbed or evolved from a reaction given its enthalpy of reaction and the mass of a reactant or product. (Example 6.4)
TOP: thermochemistry | heats of reaction
KEY: thermochemical equation | stoichiometry and heats of reaction
MSC: general chemistry
- At constant pressure and 25°C, what is DH° for the following reaction
2C2H6(g) + 7O2(g) ® 4CO2(g) + H2O(l)
if the complete consumption of 11.3 g of C2H6 liberates –586.3 kJ of heat energy?
| A) | –3120 kJ |
| B) | –1560 kJ |
| C) | –441 kJ |
| D) | –222 kJ |
| E) | –786 kJ |
ANS: A PTS: 1 DIF: moderate REF: 6.5
OBJ: Calculate the heat absorbed or evolved from a reaction given its enthalpy of reaction and the mass of a reactant or product. (Example 6.4)
- The reaction of iron with hydrochloric acid is represented by the following thermochemical equation.
Fe(s) + 2HCl(aq) ® FeCl2(aq) + H2(g); DH° = –87.9 kJ
If, in a particular experiment, 7.36 kJ of heat was released at constant pressure, what volume of H2(g), measured at STP, was produced? (R = 0.0821 L • atm/(K • mol))
| A) | 2.92 ´ 102 L |
| B) | 2.05 L |
| C) | 22.4 L |
| D) | 2.68 ´ 102 L |
| E) | 1.88 L |
ANS: E PTS: 1 DIF: moderate REF: 6.5
OBJ: Calculate the heat absorbed or evolved from a reaction given its enthalpy of reaction and the mass of a reactant or product. (Example 6.4)
TOP: thermochemistry | heats of reaction
KEY: thermochemical equation | stoichiometry and heats of reaction
MSC: general chemistry
- The reaction of iron with hydrochloric acid is represented by the following thermochemical equation.
Fe(s) + 2HCl(aq) ® FeCl2(aq) + H2(g); DH° = –87.9 kJ
In which of the following experiments would the temperature rise the most?
| A) | 2.2 g of Fe added to 1.0 L of 0.03 M HCl |
| B) | 1.1 g of Fe added to 1.0 L of 0.02 M HCl |
| C) | 4.5 g of Fe added to 1.0 L of 0.03 M HCl |
| D) | 1.1 g of Fe added to 1.0 L of 0.04 M HCl |
| E) | 0.56 g of Fe added to 1.0 L of 0.02 M HCl |
ANS: D PTS: 1 DIF: moderate REF: 6.5
OBJ: Calculate the heat absorbed or evolved from a reaction given its enthalpy of reaction and the mass of a reactant or product. (Example 6.4)
TOP: thermochemistry | heats of reaction
KEY: thermochemical equation | stoichiometry and heats of reaction
MSC: general chemistry
- How much heat is released at constant pressure if 16.9 mL of 0.694 M silver nitrate is mixed with 79.7 mL of 0.372 M potassium chloride?
AgNO3(aq) + KCl(aq) ® AgCl(s) + KNO3(aq); DH° = –65.5 kJ
| A) | –0.768 kJ |
| B) | –24.4 kJ |
| C) | –1.94 kJ |
| D) | –45.5 kJ |
| E) | –2.71 kJ |
ANS: A PTS: 1 DIF: difficult REF: 6.5
OBJ: Calculate the heat absorbed or evolved from a reaction given its enthalpy of reaction and the mass of a reactant or product. (Example 6.4)
TOP: thermochemistry | heats of reaction
KEY: thermochemical equation | stoichiometry and heats of reaction
MSC: general chemistry
- How much heat is liberated at constant pressure when 58.5 g of calcium oxide reacts with 83.9 L of carbon dioxide gas, measured at 1.00 atm pressure and 25.0°C? (R = 0.0821 L • atm/(K • mol))
CaO(s) + CO2(g) ® CaCO3(s); DH° = –178.3 kJ
| A) | –6.11 ´ 102 kJ |
| B) | –1.04 ´ 104 kJ |
| C) | –7.97 ´ 102 kJ |
| D) | –1.86 ´ 102 kJ |
| E) | –1.50 ´ 104 kJ |
ANS: D PTS: 1 DIF: difficult REF: 6.5
OBJ: Calculate the heat absorbed or evolved from a reaction given its enthalpy of reaction and the mass of a reactant or product. (Example 6.4)
TOP: thermochemistry | heats of reaction
KEY: thermochemical equation | stoichiometry and heats of reaction
MSC: general chemistry
- When 32.4 mL of liquid benzene (C6H6, d = 0.879 g/mL) reacts with 81.6 L of oxygen gas, measured at 1.00 atm pressure and 25°C, 1.19 ´ 103 kJ of heat is released at constant pressure. What is DH° for the following reaction? (R = 0.0821 L • atm/(K • mol))
2C6H6(l) + 15O2(g) ® 12CO2(g) + 6H2O(l)
| A) | –2.35 ´ 101 kJ |
| B) | –3.22 ´ 102 kJ |
| C) | –5.36 ´ 103 kJ |
| D) | –3.27 ´ 103 kJ |
| E) | –6.53 ´ 103 kJ |
ANS: E PTS: 1 DIF: difficult REF: 6.5
OBJ: Calculate the heat absorbed or evolved from a reaction given its enthalpy of reaction and the mass of a reactant or product. (Example 6.4)
TOP: thermochemistry | heats of reaction
KEY: thermochemical equation | stoichiometry and heats of reaction
MSC: general chemistry
- When 49.4 mL of 0.721 M lead(II) nitrate reacts with 99.6 mL of 0.807 M sodium chloride, 0.830 kJ of heat is released at constant pressure. What is DH° for this reaction?
Pb(NO3)2(aq) + 2NaCl(aq) ® PbCl2(s) + 2NaNO3(aq)
| A) | –23.3 kJ |
| B) | –10.3 kJ |
| C) | –4.23 kJ |
| D) | –7.15 kJ |
| E) | –20.6 kJ |
ANS: A PTS: 1 DIF: difficult REF: 6.5
OBJ: Calculate the heat absorbed or evolved from a reaction given its enthalpy of reaction and the mass of a reactant or product. (Example 6.4)
TOP: thermochemistry | heats of reaction
KEY: thermochemical equation | stoichiometry and heats of reaction
MSC: general chemistry
- A 9.020-g sample of an unknown metal M is burned in the presence of excess oxygen, producing the oxide M2O3(s) and liberating 191.5 kJ of heat at constant pressure. What is the identity of the metal?
4M(s) + 3O2(g) ® 2M2O3(s)
| Substance | DH°f (kJ/mol) |
| Yb2O3(s) | –1814.6 |
| Tb2O3(s) | –1865.2 |
| Sm2O3(s) | –1823.0 |
| Sc2O3(s) | –1908.8 |
| Y2O3(s) | –1905.3 |
ANS: B PTS: 1 DIF: difficult REF: 6.5
OBJ: Calculate the heat absorbed or evolved from a reaction given its enthalpy of reaction and the mass of a reactant or product. (Example 6.4)
TOP: thermochemistry | heats of reaction
KEY: thermochemical equation | stoichiometry and heats of reaction
MSC: general chemistry
- A 5.09-g sample of solid silver reacted in excess chlorine gas to give a 6.76-g sample of pure solid AgCl. The heat given off in this reaction was 6.00 kJ at constant pressure. Given this information, what is the enthalpy of formation of AgCl(s)?
| A) | –127 kJ/mol |
| B) | –63.6 kJ/mol |
| C) | 127 kJ/mol |
| D) | –6.00 kJ/mol |
| E) | 6.00 kJ/mol |
ANS: A PTS: 1 DIF: difficult REF: 6.5
OBJ: Calculate the heat absorbed or evolved from a reaction given its enthalpy of reaction and the mass of a reactant or product. (Example 6.4)
TOP: thermochemistry | heats of reaction
KEY: thermochemical equation | stoichiometry and heats of reaction
MSC: general chemistry
- A 2.19-g sample of solid calcium reacted in excess fluorine gas to give a 4.27-g sample of pure solid CaF2. The heat given off in this reaction was 67.0 kJ at constant pressure. Given this information, what is the enthalpy of formation of CaF2(s)?
| A) | 67.0 kJ/mol |
| B) | –67.0 kJ/mol |
| C) | –1.23 ´ 103 kJ/mol |
| D) | –613 kJ/mol |
| E) | 1.23 ´ 103 kJ/mol |
ANS: C PTS: 1 DIF: difficult REF: 6.5
OBJ: Calculate the heat absorbed or evolved from a reaction given its enthalpy of reaction and the mass of a reactant or product. (Example 6.4)
TOP: thermochemistry | heats of reaction
KEY: thermochemical equation | stoichiometry and heats of reaction
MSC: general chemistry
- The quantity of heat required to raise the temperature of a sample of a substance by 1°C is the sample’s
| A) | work. |
| B) | calorimetry. |
| C) | heat capacity. |
| D) | specific heat. |
| E) | enthalpy. |
ANS: C PTS: 1 DIF: easy REF: 6.6
OBJ: Define heat capacity and specific heat.
TOP: thermochemistry | heats of reaction KEY: calorimetry | heat capacity
MSC: general chemistry
- The units for heat capacity are
| A) | J/g. |
| B) | (J · g). |
| C) | J/°C. |
| D) | (J · °C). |
| E) | J/(g · °C). |
ANS: C PTS: 1 DIF: easy REF: 6.6
OBJ: Define heat capacity and specific heat.
TOP: thermochemistry | heats of reaction KEY: calorimetry | heat capacity
MSC: general chemistry
- The units for specific heat are
| A) | J/(g · °C). |
| B) | (J · °C). |
| C) | J/g. |
| D) | J/°C. |
| E) | (J · g). |
ANS: A PTS: 1 DIF: easy REF: 6.6
OBJ: Define heat capacity and specific heat.
TOP: thermochemistry | heats of reaction KEY: calorimetry | heat capacity
MSC: general chemistry
- The specific heat capacity of copper is 0.384 J/g×°C. What is the molar specific heat capacity of this substance? The molar mass of copper is 63.54 g/mol.
| A) | 24.4 J/mol×°C |
| B) | 0.00604 J/mol×°C |
| C) | 165 J/mol×°C |
| D) | 0.384 J/mol×°C |
| E) | 2.60 J/mol×°C |
ANS: A PTS: 1 DIF: easy REF: 6.6
OBJ: Calculate molar specific heat capacity.
TOP: thermochemistry | heats of reaction
- The heat required to raise the temperature of 52.00 g of chromium by 1°C is called its
| A) | heat of vaporization. |
| B) | specific heat. |
| C) | heat of fusion. |
| D) | entropy. |
| E) | molar heat capacity. |
ANS: E PTS: 1 DIF: easy REF: 6.6
OBJ: Define heat capacity and specific heat.
TOP: thermochemistry | heats of reaction KEY: calorimetry | heat capacity
MSC: general chemistry
- The molar heat capacity of gaseous heptane at 25.0°C is 165.2 J/(mol · °C). What is its specific heat?
| A) | 0.6065 J/(g · °C) |
| B) | 1.649 J/(g · °C) |
| C) | 6.041 ´ 10–5 J/(g · °C) |
| D) | 165.2 J/(g · °C) |
| E) | 1.655 ´ 104 J/(g · °C) |
ANS: B PTS: 1 DIF: easy REF: 6.6
OBJ: Define heat capacity and specific heat.
TOP: thermochemistry | heats of reaction KEY: calorimetry | heat capacity
MSC: general chemistry
- A 100 g sample of each of the following metals is heated from 35°C to 45°C. Which metal absorbs the lowest amount of heat energy?
| Metal | Specific Heat |
| copper | 0.385 J/(g · °C) |
| magnesium | 1.02 J/(g · °C) |
| mercury | 0.138 J/(g · °C) |
| silver | 0.237 J/(g · °C) |
| lead | 0.129 J/(g · °C) |
| A) | lead |
| B) | magnesium |
| C) | silver |
| D) | mercury |
| E) | copper |
ANS: A PTS: 1 DIF: easy REF: 6.6
OBJ: Relate the heat absorbed or evolved to the specific heat, mass, and temperature change. TOP: thermochemistry | heats of reaction
- Two metals of equal mass with different heat capacities are subjected to the same amount of heat. Which undergoes the smaller change in temperature?
| A) | The metal with the higher heat capacity undergoes the smaller change in temperature. |
| B) | Both undergo the same change in temperature. |
| C) | You need to know the initial temperatures of the metals. |
| D) | You need to know which metals you have. |
| E) | The metal with the lower heat capacity undergoes the smaller change in temperature. |
ANS: A PTS: 1 DIF: moderate REF: 6.6
OBJ: Relate the heat absorbed or evolved to the specific heat, mass, and temperature change. TOP: thermochemistry | heats of reaction
KEY: calorimetry | specific heat MSC: general chemistry
- It is relatively easy to change the temperature of a substance that
| A) | is very massive. |
| B) | is an insulator. |
| C) | has a high specific heat capacity. |
| D) | has a low specific heat capacity. |
| E) | is brittle. |
ANS: D PTS: 1 DIF: easy REF: 6.6
OBJ: Relate the heat absorbed or evolved to the specific heat, mass, and temperature change. TOP: thermochemistry | heats of reaction
KEY: calorimetry | specific heat MSC: general chemistry
- How much heat is gained by copper when 51.8 g of copper is warmed from 15.5°C to 76.4°C? The specific heat of copper is 0.385 J/(g · °C).
| A) | 3.09 ´ 102 J |
| B) | 29.41 J |
| C) | 23.45 J |
| D) | 1.21 ´ 103 J |
| E) | 1.52 ´ 103 J |
ANS: D PTS: 1 DIF: moderate REF: 6.6
OBJ: Calculate using this relation between heat and specific heat. (Example 6. 5)
TOP: thermochemistry | heats of reaction KEY: calorimetry | measuring heats of reaction
MSC: general chemistry
- Which of the following processes will result in the lowest final temperature of the metal–water mixture at equilibrium?
| A) | the addition of 100 g of silver (s = 0.237 J/(g · °C)) at 95°C to 100 mL of water at 25°C in an insulated container |
| B) | the addition of 100 g of cobalt (s = 0.418 J/(g · °C)) at 95°C to 100 mL of water at 25°C in an insulated container |
| C) | the addition of 100 g of chromium (s = 0.447 J/(g · °C)) at 95°C to 100 mL of water at 25°C in an insulated container |
| D) | the addition of 100 g of copper (s = 0.385 J/(g · °C)) at 95°C to 100 mL of water at 25°C in an insulated container |
| E) | the addition of 100 g of gold (s = 0.129 J/(g · °C)) at 95°C to 100 mL of water at 25°C in an insulated container |
ANS: E PTS: 1 DIF: easy REF: 6.6
OBJ: Calculate using this relation between heat and specific heat. (Example 6. 5)
TOP: thermochemistry | heats of reaction KEY: calorimetry | measuring heats of reaction
MSC: general chemistry
- Which of the following processes will result in the lowest final temperature of the metal–water mixture at equilibrium? The specific heat of cobalt is 0.421 J/(g · °C).
| A) | the addition of 100 g of cobalt at 95°C to 80 mL of water at 25°C in an insulated container |
| B) | the addition of 100 g of cobalt at 95°C to 100 mL of water at 25°C in an insulated container |
| C) | the addition of 100 g of cobalt at 95°C to 40 mL of water at 25°C in an insulated container |
| D) | the addition of 100 g of cobalt at 95°C to 20 mL of water at 25°C in an insulated container |
| E) | the addition of 100 g of cobalt at 95°C to 60 mL of water at 25°C in an insulated container |
ANS: B PTS: 1 DIF: moderate REF: 6.6
OBJ: Calculate using this relation between heat and specific heat. (Example 6. 5)
TOP: thermochemistry | heats of reaction KEY: calorimetry | measuring heats of reaction
MSC: general chemistry
- A 170.0-g sample of metal at 79.00°C is added to 170.0 g of H2O(l) at 14.00°C in an insulated container. The temperature rises to 16.19°C. Neglecting the heat capacity of the container, what is the specific heat of the metal? The specific heat of H2O(l) is 4.18 J/(g · °C).
| A) | 4.18 J/(g · °C) |
| B) | 120 J/(g · °C) |
| C) | 0.146 J/(g · °C) |
| D) | –0.146 J/(g · °C) |
| E) | 28.6 J/(g · °C) |
ANS: C PTS: 1 DIF: difficult REF: 6.6
OBJ: Calculate using this relation between heat and specific heat. (Example 6. 5)
TOP: thermochemistry | heats of reaction KEY: calorimetry | specific heat
MSC: general chemistry
- Exactly 105.2 J will raise the temperature of 10.0 g of a metal from 25.0°C to 60.0°C. What is the specific heat capacity of the metal?
| A) | 0.301 J/(g · °C) |
| B) | 3.33 J/(g · °C) |
| C) | 29.3 J/(g · °C) |
| D) | 25.2 J/(g · °C) |
| E) | none of these |
ANS: A PTS: 1 DIF: easy REF: 6.6
OBJ: Calculate using this relation between heat and specific heat. (Example 6. 5)
TOP: thermochemistry | heats of reaction KEY: calorimetry | specific heat
MSC: general chemistry
- A 85.9-g piece of cobalt (s = 0.421 J/(g · °C)), initially at 263.1°C, is added to 116.2 g of a liquid, initially at 24.7°C, in an insulated container. The final temperature of the metal–liquid mixture at equilibrium is 50.8°C. What is the identity of the liquid? Neglect the heat capacity of the container.
| A) | hexane (s = 2.27 J/(g · °C)) |
| B) | methanol (s = 2.53 J/(g · °C)) |
| C) | acetone (s = 2.15 J/(g · °C)) |
| D) | ethanol (s = 2.43 J/(g · °C)) |
| E) | water (s = 4.18 J/(g · °C)) |
ANS: B PTS: 1 DIF: moderate REF: 6.6
OBJ: Calculate using this relation between heat and specific heat. (Example 6. 5)
TOP: thermochemistry | heats of reaction KEY: calorimetry | specific heat
MSC: general chemistry
- A 42.9-g sample of cobalt (s = 0.421 J/(g · °C)), initially at 157.2°C, is placed in an insulated vessel containing 120.9 g of water (s = 4.18 J/(g · °C)), initially at 19.2°C. Once equilibrium is reached, what is the final temperature of the metal–water mixture? Neglect the heat capacity of the vessel.
| A) | 24.0°C |
| B) | 55.3°C |
| C) | 14.1°C |
| D) | 88.2°C |
| E) | 31.8°C |
ANS: A PTS: 1 DIF: difficult REF: 6.6
OBJ: Calculate using this relation between heat and specific heat. (Example 6. 5)
TOP: thermochemistry | heats of reaction KEY: calorimetry | specific heat
MSC: general chemistry
- How much heat must be applied to a 18.3-g sample of iron (s = 0.449 J/(g · °C)) in order to raise its temperature from 23.8°C to 356.6°C?
| A) | 2.93 ´ 103 J |
| B) | 2.73 ´ 103 J |
| C) | 1.96 ´ 102 J |
| D) | 6.09 ´ 103 J |
| E) | 1.49 ´ 102 J |
ANS: B PTS: 1 DIF: easy REF: 6.6
OBJ: Calculate using this relation between heat and specific heat. (Example 6. 5)
TOP: thermochemistry | heats of reaction KEY: calorimetry | specific heat
MSC: general chemistry
- A 94.7-g sample of silver (s = 0.237 J/(g · °C)), initially at 348.25°C, is added to an insulated vessel containing 143.6 g of water (s = 4.18 J/(g · °C)), initially at 13.97°C. At equilibrium, the final temperature of the metal–water mixture is 22.63°C. How much heat was absorbed by the water? The heat capacity of the vessel is 0.244 kJ/°C.
| A) | 5.20 kJ |
| B) | 3.09 kJ |
| C) | 7.31 kJ |
| D) | 9.12 kJ |
| E) | 129 kJ |
ANS: A PTS: 1 DIF: difficult REF: 6.6
OBJ: Calculate using this relation between heat and specific heat. (Example 6. 5)
TOP: thermochemistry | heats of reaction KEY: calorimetry | specific heat
MSC: general chemistry
- A 500-cm3 sample of 1.0 M NaOH(aq) is added to 500 cm3 of 1.0 M HCl(aq) in a Styrofoam cup, and the solution is quickly stirred. The rise in temperature (DT1) is measured. The experiment is repeated using 100 cm3 of each solution, and the rise in temperature (DT2) is measured. What conclusion can you draw about DT1 and DT2?
HCl(aq) + NaOH(aq) ® H2O(l) + NaCl(aq); DH° = –55.8 kJ
| A) | DT2 is greater than DT1. |
| B) | DT2 is equal to DT1. |
| C) | DT1 is five times as large as DT2. |
| D) | DT1 is less than DT2. |
| E) | DT2 is five times as large as DT1. |
ANS: B PTS: 1 DIF: difficult REF: 6.6
OBJ: Calculate using this relation between heat and specific heat. (Example 6. 5)
TOP: thermochemistry | heats of reaction
KEY: thermochemical equation | stoichiometry and heats of reaction
MSC: general chemistry
- In a bomb calorimeter, reactions are carried out
| A) | at 1 atm pressure and 0°C. |
| B) | at a constant pressure. |
| C) | at a constant volume. |
| D) | at a constant pressure and 25°C. |
| E) | at 1 atm pressure and 25°C. |
ANS: C PTS: 1 DIF: easy REF: 6.6
OBJ: Define calorimeter. TOP: thermochemistry | heats of reaction
KEY: calorimetry | measuring heats of reaction MSC: general chemistry
- A bomb calorimeter has a heat capacity of 2.47 kJ/K. When a 0.105-g sample of a certain hydrocarbon was burned in this calorimeter, the temperature increased by 2.14 K. Calculate the energy of combustion for 1 g of the hydrocarbon.
| A) | –5.29 J/g |
| B) | J/g |
| C) | –0.120 J/g |
| D) | J/g |
| E) | –0.560 J/g |
ANS: B PTS: 1 DIF: moderate REF: 6.6
OBJ: Calculate the enthalpy of reaction from calorimetric data (its temperature change and heat capacity). TOP: thermochemistry | heats of reaction
KEY: calorimetry | measuring heats of reaction MSC: general chemistry
- When 7.13 g of methane (CH4) is burned in a bomb calorimeter (heat capacity = 2.677 ´ 103 J/°C), the temperature rises from 24.00 to 27.08°C. How much heat is absorbed by the calorimeter?
CH4(g) + 2O2(g) ® CO2(g) + 2H2O(l); DH° = –1283.8 kJ
| A) | 562 kJ |
| B) | 3.66 ´ 103 kJ |
| C) | 8.24 kJ |
| D) | 571 kJ |
| E) | 1.28 ´ 103 kJ |
ANS: C PTS: 1 DIF: difficult REF: 6.6
OBJ: Calculate the enthalpy of reaction from calorimetric data (its temperature change and heat capacity). TOP: thermochemistry | heats of reaction
KEY: calorimetry | heat capacity MSC: general chemistry
- When 0.0600 mol of HCl(aq) is reacted with 0.0600 mol of NaOH(aq) in 50.0 mL of water, the temperature of the solution increases by 15.1°C. What is the enthalpy of reaction for the following thermochemical equation?
HCl(aq) + NaOH(aq) ® NaCl(aq) + H2O(l)
Assume that the heat capacity of the solution and calorimeter is 221.3 J/°C.
| A) | –0.201 kJ |
| B) | 55.8 kJ |
| C) | –3.35 kJ |
| D) | –55.8 kJ |
| E) | 3.35 kJ |
ANS: D PTS: 1 DIF: moderate REF: 6.6
OBJ: Calculate the enthalpy of reaction from calorimetric data (its temperature change and heat capacity). TOP: thermochemistry | heats of reaction
KEY: calorimetry | measuring heats of reaction MSC: general chemistry
- When 50.0 mL of 1.20 M of HCl(aq) is combined with 50.0 mL of 1.30 M of NaOH(aq) in a coffee-cup calorimeter, the temperature of the solution increases by 8.01°C. What is the change in enthalpy for this balanced reaction?
HCl(aq) + NaOH(aq) ® NaCl(aq) + H2O(l)
Assume that the solution density is 1.00 g/mL and the specific heat capacity of the solution is 4.18 J/g×°C.
| A) | –55.8 kJ |
| B) | 55.8 kJ |
| C) | 51.5 kJ |
| D) | –51.5 kJ |
| E) | –26.8 kJ |
ANS: A PTS: 1 DIF: moderate REF: 6.6
OBJ: Calculate the enthalpy of reaction from calorimetric data (its temperature change and heat capacity). TOP: thermochemistry | heats of reaction
- Combustion of 7.21 g of liquid benzene (C6H6) causes a temperature rise of 50.3°C in a constant-pressure calorimeter that has a heat capacity of 5.99 kJ/°C. What is DH for the following reaction?
C6H6(l) + O2(g) ® 6CO2(g) + 3H2O(l)
| A) | –302 kJ/mol |
| B) | 41.8 kJ/mol |
| C) | –41.8 kJ/mol |
| D) | –3.27 ´ 103 kJ/mol |
| E) | 302 kJ/mol |
ANS: D PTS: 1 DIF: moderate REF: 6.6
OBJ: Calculate the enthalpy of reaction from calorimetric data (its temperature change and heat capacity). TOP: thermochemistry | heats of reaction
KEY: calorimetry | measuring heats of reaction MSC: general chemistry
- Given:
Pb(s) + PbO2(s) + 2H2SO4(l) ® 2PbSO4(s) + 2H2O(l); DH° = –509.2 kJ
SO3(g) + H2O(l) ® H2SO4(l); DH° = –130. kJ
determine DH° for the following thermochemical equation.
Pb(s) + PbO2(s) + 2SO3(g) ® 2PbSO4(s)
| A) | 3.77 ´ 103 kJ |
| B) | –521 kJ |
| C) | –3.77 ´ 103 kJ |
| D) | –639 kJ |
| E) | –769 kJ |
ANS: E PTS: 1 DIF: moderate REF: 6.7
OBJ: Apply Hess’s law to obtain the enthalpy change for one reaction from the enthalpy changes of a number of other reactions. (Example 6.7)
TOP: thermochemistry | heats of reaction KEY: Hess’s law MSC: general chemistry
- Given:
Fe2O3(s) + 3CO(g) ® 2Fe(s) + 3CO2(g); DH° = –26.8 kJ
FeO(s) + CO(g) ® Fe(s) + CO2(g); DH° = –16.5 kJ
determine DH° for the following thermochemical equation.
Fe2O3(s) + CO(g) ® 2FeO(s) + CO2(g)
| A) | 6.2 kJ |
| B) | 10.3 kJ |
| C) | 22.7 kJ |
| D) | –10.3 kJ |
| E) | –43.3 kJ |
ANS: A PTS: 1 DIF: moderate REF: 6.7
OBJ: Apply Hess’s law to obtain the enthalpy change for one reaction from the enthalpy changes of a number of other reactions. (Example 6.7)
TOP: thermochemistry | heats of reaction KEY: Hess’s law MSC: general chemistry
- The overall chemical equation resulting from the sum of the following three steps is
2C(s) + 2H2O(g) ® 2CO(g) + 2H2(g)
CO(g) + H2O(g) ® CO2(g) + H2(g)
CO(g) + 3H2(g) ® CH4(g) + H2O(g)
| A) | 2C(s) + 2H2O(g) ® CO2(g) + CH4(g) |
| B) | 2C(s) + 3H2O(g) ® CO(g) + CO2(g) + 3H2(g) |
| C) | 2C(s) + H2O(g) + H2(g)® CO(g) + CH4(g) |
| D) | 2CO(g) + 2H2(g) ® CH4(g) + CO2(g) |
| E) | 2C(s) + CH4(g) + 3H2O(g) ® 3CO(g) + 5H2(g) |
ANS: A PTS: 1 DIF: easy REF: 6.7
OBJ: Apply Hess’s law to obtain the overall reaction.
TOP: thermochemistry | heats of reaction
- Using the following data, calculate the standard enthalpy of reaction for the coal gasification process 2C(s) + 2H2O(g) ® CH4(g) + CO2(g).
C(s) + H2O(g) ® CO(g) + H2(g); DH° = +131.3 kJ
CO(g) + H2O(g) ® CO2(g) + H2(g); DH° = –41.2 kJ
CO(g) + 3H2(g) ® CH4(g) + H2O(g); DH° = –206.1 kJ
| A) | –116.0 kJ |
| B) | 378.6 kJ |
| C) | +15.3 kJ |
| D) | –157.2 kJ |
| E) | –378.6 kJ |
ANS: C PTS: 1 DIF: moderate REF: 6.7
OBJ: Apply Hess’s law to obtain the enthalpy change for one reaction from the enthalpy changes of a number of other reactions. (Example 6.7)
TOP: thermochemistry | heats of reaction KEY: Hess’s law MSC: general chemistry
- Given the following data, calculate the standard enthalpy of reaction for the conversion of buckminsterfullerene (C60) into diamond:
C(graphite) ® C(diamond); DH° = +1.897 kJ
60C(graphite) ® C60(fullerene); DH° = +2193 kJ
| A) | -35 kJ |
| B) | 35 kJ |
| C) | -2191 kJ |
| D) | 2191 kJ |
| E) | 38 kJ |
ANS: A PTS: 1 DIF: moderate REF: 6.7
OBJ: Apply Hess’s law to obtain the enthalpy change for one reaction from the enthalpy changes of a number of other reactions. (Example 6.7)
TOP: thermochemistry | heats of reaction
- Using two or more of the following,
N2(g) + O2(g) ® N2O3(s); DH° = 83.7 kJ
N2(g) + O2(g) ® 2NO(g); DH° = 180.4 kJ
N2(g) + O2(g) ® NO2(g); DH° = 33.2 kJ
N2(g) + H2(g) ® NH3(g); DH° = -45.9 kJ
determine DH° for the following reaction.
NO(g) + NO2(g) ® N2O3(g)
| A) | –39.7 kJ |
| B) | 24.3 kJ |
| C) | –207.1 kJ |
| D) | 39.7 kJ |
| E) | 207.1 kJ |
ANS: A PTS: 1 DIF: moderate REF: 6.7
OBJ: Apply Hess’s law to obtain the enthalpy change for one reaction from the enthalpy changes of a number of other reactions. (Example 6.7)
TOP: thermochemistry | heats of reaction
- Consider the following changes at constant temperature and pressure:
| H2O(s) ® H2O(l); DH1 |
| H2O(l) ® H2O(g); DH2 |
| H2O(g) ® H2O(s); DH3 |
Using Hess’s law, the sum DH1 + DH2 + DH3 is
| A) | equal to zero. |
| B) | sometimes greater than zero and sometimes less than zero. |
| C) | less than zero. |
| D) | cannot be determined without numerical values for DH. |
| E) | greater than zero. |
ANS: A PTS: 1 DIF: moderate REF: 6.7
OBJ: Apply Hess’s law to obtain the enthalpy change for one reaction from the enthalpy changes of a number of other reactions. (Example 6.7)
TOP: thermochemistry | heats of reaction KEY: Hess’s law MSC: general chemistry
- Given the following thermochemical data at 25°C and 1 atm pressure,
O2(g) + 2B(s) ® B2O3(s); DH° = –1264 kJ
O3(g) + 2B(s) ® B2O3(s); DH° = –1406 kJ
determine DH° for the following reaction at 25°C and 1 atm pressure.
3O2(g) ® 2O3(g)
| A) | –980 kJ/mol |
| B) | +284 kJ/mol |
| C) | +980 kJ/mol |
| D) | –2670 kJ/mol |
| E) | –284 kJ/mol |
ANS: B PTS: 1 DIF: moderate REF: 6.7
OBJ: Apply Hess’s law to obtain the enthalpy change for one reaction from the enthalpy changes of a number of other reactions. (Example 6.7)
TOP: thermochemistry | heats of reaction KEY: Hess’s law MSC: general chemistry
- What is the standard enthalpy of formation of liquid methylamine (CH3NH2)?
C(s) + O2(g) ® CO2(g); DH° = –393.5 kJ
2H2O(l) ® 2H2(g) + O2(g); DH° = 571.6 kJ
N2(g) + O2(g) ® NO2(g); DH° = 33.10 kJ
4CH3NH2(l) + 13O2(g) ® 4CO2(g) + 4NO2(g) + 10H2O(l); DH° = –4110.4 kJ
| A) | +3899.2 kJ/mol |
| B) | –3899.2 kJ/mol |
| C) | –47.3 kJ/mol |
| D) | +47.3 kJ/mol |
| E) | +3178.4 kJ |
ANS: C PTS: 1 DIF: difficult REF: 6.7
OBJ: Apply Hess’s law to obtain the enthalpy change for one reaction from the enthalpy changes of a number of other reactions. (Example 6.7)
TOP: thermochemistry | heats of reaction KEY: Hess’s law MSC: general chemistry
- Given that
O(g) + e– ® O–(g); DH = –142 kJ
O(g) + 2e– ® O2–(g); DH = 702 kJ
the enthalpy change for the reaction represented by the equation
O–(g) + e– ® O2–(g) is
| A) | 0 kJ. |
| B) | –560 kJ. |
| C) | –844 kJ. |
| D) | 844 kJ. |
| E) | 560 kJ. |
ANS: D PTS: 1 DIF: moderate REF: 6.7
OBJ: Apply Hess’s law to obtain the enthalpy change for one reaction from the enthalpy changes of a number of other reactions. (Example 6.7)
TOP: thermochemistry | heats of reaction KEY: Hess’s law MSC: general chemistry
- Which of the following has a standard enthalpy of formation value of zero at 25°C?
| A) | Cl(g) |
| B) | Cl2(l) |
| C) | Cl2(g) |
| D) | Cl(s) |
| E) | Cl2(s) |
ANS: C PTS: 1 DIF: easy REF: 6.8
OBJ: Define standard state and reference form.
TOP: thermochemistry | heats of reaction KEY: standard enthalpies of formation
MSC: general chemistry
- Which of the following has a standard enthalpy of formation value of zero at 25°C?
| A) | O2(g) |
| B) | O3(g) |
| C) | O2(l) |
| D) | O(g) |
| E) | O2(s) |
ANS: A PTS: 1 DIF: easy REF: 6.8
OBJ: Define standard state and reference form.
TOP: thermochemistry | heats of reaction KEY: standard enthalpies of formation
MSC: general chemistry
- All of the following have a standard enthalpy of formation value of zero at 25°C except
| A) | C(s). |
| B) | Ne(g). |
| C) | Fe(s). |
| D) | F2(g). |
| E) | CO(g). |
ANS: E PTS: 1 DIF: easy REF: 6.8
OBJ: Define standard state and reference form.
TOP: thermochemistry | heats of reaction KEY: standard enthalpies of formation
MSC: general chemistry
- Which substance has a standard enthalpy of formation equal to zero at 25°C?
| A) | C2H6(g) |
| B) | Br2(g) |
| C) | Br2(l) |
| D) | Br2(s) |
| E) | C2H6(l) |
ANS: C PTS: 1 DIF: easy REF: 6.8
OBJ: Define standard state and reference form.
TOP: thermochemistry | heats of reaction KEY: standard enthalpies of formation
MSC: general chemistry
- Which of the following species does not have a standard enthalpy of formation equal to zero at 25°C?
| A) | Cl2(l) |
| B) | N2(g) |
| C) | Fe(s) |
| D) | H+(aq) |
| E) | S8(s) |
ANS: A PTS: 1 DIF: easy REF: 6.8
OBJ: Define standard state and reference form.
TOP: thermochemistry | heats of reaction KEY: standard enthalpies of formation
MSC: general chemistry
- Which of the following has a standard enthalpy of formation value of zero at 25°C?
| A) | C6H12O6(s) |
| B) | S8(s) |
| C) | FeSO4(s) |
| D) | H2O(l) |
| E) | FeSO4(aq) |
ANS: B PTS: 1 DIF: easy REF: 6.8
OBJ: Define standard state and reference form.
TOP: thermochemistry | heats of reaction KEY: standard enthalpies of formation
MSC: general chemistry
- Which of the following reactions corresponds to the thermochemical equation for the standard enthalpy of formation of solid lead (II) nitrate?
| A) | Pb2+(aq) + 2NO3–(aq) ® Pb(NO3)2(s) |
| B) | Pb(OH)2(s) + 2HNO3(aq) ® Pb(NO3)2(s) + 2H2O(l) |
| C) | Pb(s) + N2(g) + 3O2(g) ® Pb(NO3)2(s) |
| D) | Pb(s) + 2HNO3(aq) ® Pb(NO3)2(s) + H2(g) |
| E) | Pb(s) + 2N(g) + 6O(g) ® Pb(NO3)2(s) |
ANS: C PTS: 1 DIF: easy REF: 6.8
OBJ: Define standard enthalpy of formation.
TOP: thermochemistry | heats of reaction KEY: standard enthalpies of formation
MSC: general chemistry
- The standard enthalpy change for which of the following processes corresponds to the standard enthalpy of formation of solid cesium fluoride?
| A) | Cs(s) + F2(s) ® CsF(s) |
| B) | Cs(g) + F2(g) ® CsF(g) |
| C) | Cs(g) + F(g) ® CsF(s) |
| D) | Cs(s) + F2(g) ® CsF(s) |
| E) | Cs(s) + F2(s) ® CsF(g) |
ANS: D PTS: 1 DIF: easy REF: 6.8
OBJ: Define standard enthalpy of formation.
TOP: thermochemistry | heats of reaction KEY: standard enthalpies of formation
MSC: general chemistry
- The enthalpy change at 1 atm of which reaction corresponds to the standard enthalpy of formation of solid potassium bromate, KBrO3?
| A) | K(s) + Br(g) + 3O(g) ® KBrO3(s) |
| B) | K(g) + Br(g) + 3O(g) ® KBrO3(s) |
| C) | K(g) + Br2(g) + O2(g) ® KBrO3(s) |
| D) | K(s) + Br2(l) + O2(g) ® KBrO3(s) |
| E) | K(s) + Br2(g) + O2(g) ® KBrO3(s) |
ANS: D PTS: 1 DIF: easy REF: 6.8
OBJ: Define standard enthalpy of formation.
TOP: thermochemistry | heats of reaction KEY: standard enthalpies of formation
MSC: general chemistry
- For which of the following equations is the enthalpy change at 1 atm pressure equal to the standard enthalpy of formation of liquid formic acid, HCOOH?
| A) | C(g) + 2H(g) + 2O(g) ® HCOOH(l) |
| B) | C(s) + 2H(g) + 2O(g) ® HCOOH(l) |
| C) | C(s) + H2(g) + O2(g) ® HCOOH(l) |
| D) | CO(g) + H2O(l) ® HCOOH(l) |
| E) | CO2(g) + H2(g) ® HCOOH(l) |
ANS: C PTS: 1 DIF: easy REF: 6.8
OBJ: Define standard enthalpy of formation.
TOP: thermochemistry | heats of reaction KEY: standard enthalpies of formation
MSC: general chemistry
- The balanced equation representing the standard enthalpy of formation reaction for NH3(g) is
| A) | N(g) + H2(g) ® NH3(g). |
| B) | N2(g) + 3H(g) ® NH3(g). |
| C) | N(g) + 3H(g) ® NH3(g). |
| D) | N2(g) + H2(g) ® NH3(g). |
| E) | N2(g) + H2(g) ® NH3(g). |
ANS: D PTS: 1 DIF: easy REF: 6.8
OBJ: Define standard enthalpy of formation.
TOP: thermochemistry | heats of reaction
- The enthalpy change at 1 atm of which reaction corresponds to the standard enthalpy of formation of solid magnesium nitrate, Mg(NO3)2?
| A) | Mg2+(g) + 2NO3–(g) ® Mg(NO3)2(s) |
| B) | Mg(s) + N2(g) + 3O2(g) ® Mg(NO3)2(s) |
| C) | Mg(g) + 2N(g) + 6O(g) ® Mg(NO3)2(s) |
| D) | Mg(s) + N2(g) + 2O3(g) ® Mg(NO3)2(s) |
| E) | Mg2+(aq) + 2NO3–(aq) ® Mg(NO3)2(s) |
ANS: B PTS: 1 DIF: easy REF: 6.8
OBJ: Define standard enthalpy of formation.
TOP: thermochemistry | heats of reaction KEY: standard enthalpies of formation
MSC: general chemistry
- Which of the following reactions corresponds to the thermochemical equation for the standard enthalpy of formation of N,N-diethyl-m-toluamide, C12H17NO(l), the active ingredient in some insect repellents?
| A) | 12C(l) + 17H(l) + N(l) + O(l) ® C12H17NO(l) |
| B) | 12C(g) + 17H(g) + N(g) + O(g) ® C12H17NO(g) |
| C) | 12C(s) + 17H(g) + N(g) + O(g) ® C12H17NO(l) |
| D) | 12C(s) + H2(g) + N2(g) + O2(g) ® C12H17NO(l) |
| E) | 12C(g) + 17H(g) + N(g) + O(g) ® C12H17NO(l) |
ANS: D PTS: 1 DIF: easy REF: 6.8
OBJ: Define standard enthalpy of formation.
TOP: thermochemistry | heats of reaction KEY: standard enthalpies of formation
MSC: general chemistry
- What is DH° for the following phase change?
KCl(s) ® KCl(l)
| Substance | DH°f (kJ/mol) |
| KCl(s) | –436.68 |
| KCl(l) | –421.79 |
| A) | 858.47 kJ |
| B) | 14.89 kJ |
| C) | –858.47 kJ |
| D) | –14.89 kJ |
| E) | 0 kJ |
ANS: B PTS: 1 DIF: moderate REF: 6.8
OBJ: Calculate the heat of a phase transition using standard enthalpies of formation for the different phases. (Example 6.8) TOP: thermochemistry | heats of reaction
KEY: standard enthalpies of formation MSC: general chemistry
- A 34.5-L sample of a gaseous hydrocarbon, measured at 1.00 atm pressure and 25.0°C, is burned in excess oxygen, liberating 2.20 ´ 103 kJ of heat at constant pressure. What is the identity of the hydrocarbon? (R = 0.0821 L · atm/(K · mol))
| Substance | DH°f (kJ/mol) |
| CO2(g) | –393.5 |
| H2O(l) | –285.8 |
| A) | propylene (C3H6, DH°f = 20.41 kJ/mol) |
| B) | ethylene (C2H4, DH°f = 52.47 kJ/mol) |
| C) | acetylene (C2H2, DH°f = 226.73 kJ/mol) |
| D) | ethane (C2H6, DH°f = –84.68 kJ/mol) |
| E) | propane (C3H8, DH°f = –104.7 kJ/mol) |
ANS: D PTS: 1 DIF: difficult REF: 6.8
OBJ: Calculate the heat (enthalpy) of reaction from the standard enthalpies of formation of the substances in the reaction. (Example 6.9)
TOP: thermochemistry | heats of reaction KEY: standard enthalpies of formation
MSC: general chemistry
- What is DH° of the following reaction?
CO2(g) + 2CH4(g) ® C3H8(g) + O2(g)
| Substance | DH°f (kJ/mol) |
| CO2(g) | –393.5 |
| CH4(g) | –74.9 |
| C3H8(g) | –104.7 |
| A) | –348.4 kJ |
| B) | –573.1 kJ |
| C) | 438.6 kJ |
| D) | 348.4 kJ |
| E) | –648.0 kJ |
ANS: C PTS: 1 DIF: easy REF: 6.8
OBJ: Calculate the heat (enthalpy) of reaction from the standard enthalpies of formation of the substances in the reaction. (Example 6.9)
TOP: thermochemistry | heats of reaction KEY: standard enthalpies of formation
MSC: general chemistry
- From the following information, determine DH°f of malonic acid, CH2(COOH)2(s).
CH2(COOH)2(s) + 2O2(g) ® 3CO2(g) + 2H2O(l); DH° = –861.0 kJ
| Substance | DH°f (kJ/mol) |
| CO2(g) | –393.5 |
| H2O(l) | –285.8 |
| A) | 2613 kJ |
| B) | 891.1 kJ |
| C) | -1540.3 kJ |
| D) | -2613.1 kJ |
| E) | -891.1 kJ |
ANS: E PTS: 1 DIF: moderate REF: 6.8
OBJ: Calculate the heat (enthalpy) of reaction from the standard enthalpies of formation of the substances in the reaction. (Example 6.9)
TOP: thermochemistry | heats of reaction KEY: standard enthalpies of formation
MSC: general chemistry
- At 25°C, when 1.00 g of sulfur is burned at constant pressure in excess oxygen to give SO2(g), 9.28 kJ of heat is liberated. What is the enthalpy of formation of SO2(g)?
| A) | 9.28 kJ/mol |
| B) | –594 kJ/mol |
| C) | 298 kJ/mol |
| D) | –9.28 kJ/mol |
| E) | –298 kJ/mol |
ANS: E PTS: 1 DIF: difficult REF: 6.8
OBJ: Calculate the heat (enthalpy) of reaction from the standard enthalpies of formation of the substances in the reaction. (Example 6.9)
TOP: thermochemistry | heats of reaction KEY: standard enthalpies of formation
MSC: general chemistry
- What is the standard enthalpy of formation of liquid butyraldehyde, CH3CH2CH2CHO(l)?
CH3CH2CH2CHO(l) + O2(g) ® 4H2O(l) + 4CO2(g); DH° = –2471.8 kJ
| Substance | DH°f (kJ/mol) |
| CO2(g) | –393.5 |
| H2O(l) | –285.8 |
| A) | –245.4 kJ/mol |
| B) | +245.4 kJ/mol |
| C) | –1792.5 kJ/mol |
| D) | –3151.1 kJ/mol |
| E) | +3151.1 kJ/mol |
