Name: Class: _ Date: _ ID: A Chpter 17 review Multiple Choice Identify the choice that best completes the statement or answers the question. 1. Which of these phase changes is an endothermic process? a. condensation b. evaporation c. freezing d. All phase changes are endothermic. 2. During an endothermic chemical reaction, what is the source of energy that causes the reaction to continue? a. materials that are part of the system b. reactants involved in the reaction c. chemical bonds of the reaction products d. materials in the surroundings of the system 3. How do calories and joules differ from one another? a. They are two different measures of amounts of energy. b. Calories measure energy and joules measure heat flow. c. Joules are used in chemistry and calories are used in biology. d. Joule and calorie are two different names for the same unit of energy. 4. What happens when energy is changed from one form to another? a. Some of the energy is lost entirely. b. All of the energy can be accounted for. c. A physical change to a substance occurs. d. All of the energy is changed to a useful form. 5. What factor must be constant for enthalpy to be equivalent to the total flow of heat? a. mass b. pressure c. temperature d. volume 6. Which statement correctly describes the energy of the chemical bonds of the reactants in an exothermic reaction? a. equal to the energy stored in the bonds of the products b. greater than the energy stored in the bonds of the products c. less than the energy stored in the bonds of the products d. independent of the energy stored in the bonds of the products 7. What do you know about a chemical reaction if the value of ΔH is positive? a. The reaction is exothermic. b. The reaction is endothermic. c. The reaction occurs without the addition of energy. d. The reaction cannot occur at room temperature. 1
Name: ID: A 8. One mole of hydrogen is burned in oxygen to produce water in the gas phase, ΔH = 285.8 kj. What is the energy change when 1 mole of water, in the gas phase, decomposes to form hydrogen and oxygen? a. 142.9 kj of heat is absorbed. b. 285.8 kj of heat is absorbed. c. 142.9 kj of heat is released. d. 285.8 kj of heat is released. 9. What is the amount of heat required to raise the temperature of 200.0 g of aluminum by 10 C? (specific heat of aluminum = 0.21 cal ) a. 420 cal b. 4200 cal c. 42,000 cal d. 420,000 cal 10. What is the specific heat of a substance if 1560 cal are required to raise the temperature of a 312-g sample by 15 C? a. 0.033 cal b. 0.33 cal c. 0.99 cal d. 1.33 cal 11. How many kilocalories of heat are required to raise the temperature of 225 g of aluminum from 20 C to 100 C? (specific heat of aluminum = 0.21 cal ) a. 0.59 kcal b. 3.8 kcal c. 38 kcal d. 85 kcal 12. A 100 gram piece of heated iron cools from 50 to 20 C. How much heat is released to the surroundings? a. 300 J of heat are released to the surroundings. b. 300 cal of heat are released to the surroundings. c. The amount of heat cannot be calculated because the heat capacity is not known. d. The amount of heat cannot be calculated because there is no closed system. 13. How can you describe the specific heat of olive oil if it takes approximately 420 J of heat to raise the temperature of 7 g of olive oil by 30 C? a. greater than the specific heat of water b. less than the specific heat of water c. equal to the specific heat of water d. Not enough information is given. 2
Name: ID: A 14. The specific heat of silver is 0.24 from 25.0 C to 27.5 C? a. 2.62 J b. 0.14 J c. 45.5 J d. 0.022 J J. How many joules of energy are needed to warm 4.37 g of silver 15. How much ice at 0 C could be melted by the addition of 15 kj of heat? (ΔH fus = 6.01kJ/mol) a. 0.4 g b. 2.5 g c. 7.2 g d. 45 g 16. By what quantity must the heat capacity of an object be divided to obtain the specific heat of that material? a. its mass b. its volume c. its temperature d. its energy 17. How much ammonia (NH 3 ) could be melted by the addition of 1 kj of heat, if the temperature of the liquid is at the melting point? (ΔH fus = 5.66 kj/mol) a. 0.33 g b. 1.8 g c. 3.0 g d. 39.6 g 18. What are the standard conditions for determining heat of formation? a. 0 C and 101 kpa b. 25 C and 101 kpa c. 0 C and 0 kpa d. 25 C and 22.4 kpa 19. A chunk of ice whose temperature is 20 C is added to an insulated cup filled with water at 0 C. What happens in the cup? a. The ice melts until it reaches the temperature of the water. b. The water cools until it reaches the temperature of the ice. c. Some of the water freezes, so the chunk of ice gets larger. d. Some of the ice melts and the water cools at the same time. 20. Calculate the energy required to produce 7.00 mol Cl 2 O 7 on the basis of the following balanced equation. 2Cl 2 (g) + 7O 2 (g) + 130 kcal 2Cl 2 O 7 (g) a. 7.00 kcal b. 65 kcal c. 130 kcal d. 455 kcal 3
Name: ID: A 21. Calculate ΔH for the following reaction. C 2 H 4 (g) + H 2 (g) C 2 H 6 (g) (ΔH f 0 for C 2 H 4 (g) = 52.5 kj/mol; ΔH f 0 for C 2 H 6 (g) = 84.7 kj/mol) a. 137.2 kj b. 32.2 kj c. 32.2 kj d. 137.2 kj 22. Calculate the energy released when 24.8 g Na 2 O reacts in the following reaction. Na 2 O(s) + 2HI(g) 2NaI(s) + H 2 O(l) ΔH = 120.00 kcal a. 0.207 kcal b. 2.42 kcal c. 48.0 kcal d. 3.00 10 2 kcal 23. What is the heat of solution? a. the amount of heat required to change a solid into a liquid b. the amount of heat absorbed or released when a solid dissolves c. the amount of heat required to change a vapor into a liquid d. the amount of heat released when a vapor changes into a liquid 24. When 1.0 g of solid NaOH (ΔH soln = 445.1 kj/mol) dissolves in 10 L of water, how much heat is released? a. 445.1 kj b. 405.1 kj c. 11.1 J d. 11.1 kj 25. Which of these statements correctly describes Hess s law of heat summation? a. It is used to calculate ΔH for complicated chemical reactions. b. It can be used to calculate the heat of formation of an element. c. It explains why a calorimeter can be used to determine the heat of reaction. d. It describes the thermal changes during the vaporization of solids. 4
ID: A Chpter 17 review Answer Section MULTIPLE CHOICE 1. ANS: B PTS: 1 DIF: L2 REF: p. 558 OBJ: 17.1.2 Explain how the energy of the universe before a chemical or physical process is related to the energy of the universe after a chemical or physical process. 2. ANS: D PTS: 1 DIF: L2 REF: p. 557 OBJ: 17.1.2 Explain how the energy of the universe before a chemical or physical process is related to the energy of the universe after a chemical or physical process. 3. ANS: A PTS: 1 DIF: L2 REF: p. 558 OBJ: 17.1.2 Explain how the energy of the universe before a chemical or physical process is related to the energy of the universe after a chemical or physical process. 4. ANS: B PTS: 1 DIF: L1 REF: p. 557 OBJ: 17.1.1 Explain the ways in which energy changes can occur. 5. ANS: B PTS: 1 DIF: L1 REF: p. 562 OBJ: 17.2.1 Describe how you measure the change in enthalpy of a reaction. 6. ANS: B PTS: 1 DIF: L2 REF: p. 566 7. ANS: B PTS: 1 DIF: L2 REF: p. 566 8. ANS: B PTS: 1 DIF: L2 REF: p. 566 9. ANS: A PTS: 1 DIF: L2 REF: p. 560 10. ANS: B PTS: 1 DIF: L2 REF: p. 561 11. ANS: B PTS: 1 DIF: L2 REF: p. 561 12. ANS: C PTS: 1 DIF: L2 REF: p. 559 13. ANS: B PTS: 1 DIF: L2 REF: p. 560 1
ID: A 14. ANS: A PTS: 1 DIF: L2 REF: p. 560 15. ANS: D PTS: 1 DIF: L2 REF: p. 570 OBJ: 17.3.1 Compare the quantity of heat absorbed by a melting solid to the quantity of heat released when the liquid solidifies. 16. ANS: A PTS: 1 DIF: L2 REF: p. 560 17. ANS: C PTS: 1 DIF: L2 REF: p. 570 OBJ: 17.3.1 Compare the quantity of heat absorbed by a melting solid to the quantity of heat released when the liquid solidifies. 18. ANS: B PTS: 1 DIF: L2 REF: p. 580 OBJ: 17.4.1 Identify two ways that you can determine the heat of reaction when it cannot be directly measured. 19. ANS: C PTS: 1 DIF: L2 REF: p. 569 OBJ: 17.3.1 Compare the quantity of heat absorbed by a melting solid to the quantity of heat released when the liquid solidifies. 20. ANS: D PTS: 1 DIF: L2 REF: p. 566 21. ANS: A PTS: 1 DIF: L3 REF: p. 566 22. ANS: C PTS: 1 DIF: L2 REF: p. 566 23. ANS: B PTS: 1 DIF: L1 REF: p. 574 OBJ: 17.3.3 Describe thermochemical changes that occur when a solution forms. 24. ANS: D PTS: 1 DIF: L2 REF: p. 575 OBJ: 17.3.3 Describe thermochemical changes that occur when a solution forms. 25. ANS: A PTS: 1 DIF: L1 REF: p. 578 OBJ: 17.4.1 Identify two ways that you can determine the heat of reaction when it cannot be directly measured. 2