Name Energy Test period Date

Transcription

1 Name Energy Test period Date 1. The temperature 30. K expressed in degrees Celsius is 1) 243ºC 2) 243ºC 3) 303ºC 4) 303ºC 2. The potential energy diagram for a chemical reaction is shown below. 4. A sample of water is heated from 10.0ºC to 15.0ºC by the addition of 126 Joules of heat. What is the mass of the water? 1) 5.00 g 2) 6.00 g 3) 30.0 g 4) g 5. What is the amount of heat, in joules, required to increase the temperature of a 49.5-gram sample of water from 22 C to 66 C? 1) 2.2 x 10 3 J 2) 4.6 x 10 3 J 3) 9.1 x 10 3 J 4) 1.4 x 10 4 J 6. The phase change represented by the equation I2(s) I2(g) Each interval on the axis labeled "Potential Energy (kj)" represents 40 kilojoules. What is the heat of reaction? 1) 120kJ 2) 40kJ 3) +40kJ 4) +160kJ 3. Base your answer to the following question on the potential energy diagram of a chemical reaction shown below. is called 1) sublimation 2) condensation 3) melting 4) boiling 7. What amount of heat is required to completely melt a gram sample of H2O(s) at 0 C? 1) 334 J 2) 2260 J 3) J 4) J Which arrow represents the activation energy for the forward reaction? 1) A 2) B 3) C 4) D

2 8. The graph below represents the uniform cooling of a substance, starting with the substance as a gas above its boiling point. During which interval is the substance completely in the liquid phase? 1) AB 2) BC 3) CD 4) DE 9. At which Celsius temperature does lead change from a solid to a liquid? 1) 874 C 2) 601 C 3) 328 C 4) 0 C 10. The cooling curve below represents the uniform cooling of a substance, starting at a temperature above its boiling point. During which time interval does the substance exist as both a liquid and a solid? 1) min 2 to min 4 2) min 4 to min 5 3) min 5 to min 7 4) min 7 to min 9

3 Base your answers to questions 11 and 12 on the potential energy diagram below, which represents the reaction: 15. Given the potential energy diagram of a chemical reaction: A + B C + energy. 11. Which numbered interval will change with the addition of a catalyst to the system? 1) 1 2) 2 3) 3 4) Which statement correctly describes this reaction? 1) It is endothermic and energy is absorbed. 2) It is endothermic and energy is released. 3) It is exothermic and energy is absorbed. 4) It is exothermic and energy is released. Which arrow represents the potential energy of the reactants? 1) A 2) B 3) C 4) D 16. The graph below represents the relationship between temperature and time as heat is added uniformly to a substance, starting when the substance is a solid below its melting point. 13. Based on Reference Table I, which reaction is endothermic? 1) NaOH(s) Na + (aq) + OH (aq) 2) NH4Cl(s) NH4 + (aq) + Cl (aq) 3) CO(g) + O2(g) CO2(g) 4) CH4(g) + 2 O2(g) CO2(g) + 2 H2O( ) Which portions of the graph represent times when heat is absorbed and potential energy increases while kinetic energy remains constant? 1) A and B 2) B and D 3) A and C 4) C and D 14. According to Reference Table I, what is the heat of reaction for the formation of two moles of H2O( ) from hydrogen and oxygen gas at 1 atmosphere and 298 K? 1) kj 2) kj 3) 55.8 kj 4) kj 17. In a chemical reaction, the difference between the potential energy of the products and the potential energy of the reactants is the 1) heat of reaction 2) heat of fusion 3) free energy 4) activation energy

4 18. A 36-gram sample of water has an initial temperature of 22 C. After the sample absorbs 1200 joules of heat energy, the final temperature of the sample is 1) 8.0 C 2) 14 C 3) 30. C 4) 55 C 24. The graph below represents the uniform heating of a substance, starting below its melting point, when the substance is solid. 19. Which statement correctly describes an endothermic chemical reaction? 1) The products have higher potential energy than the reactants, and the H is negative. 2) The products have higher potential energy than the reactants, and the H is positive. 3) The products have lower potential energy than the reactants, and the H is negative. 4) The products have lower potential energy than the reactants, and the H is positive. 20. Which substance will sublime at 298 K? 1) CO2(s) 2) Al(s) 3) Si(s) 4) KOH(s) 21. Which term represents a form of energy? 1) heat 2) degree 3) kilocalorie 4) temperature Which line segments represent an increase in average kinetic energy? 1) and 2) and 3) and 4) and 25. Which form of energy is associated with the random motion of the particles in a sample of water? 1) chemical energy 2) electrical energy 3) nuclear energy 4) thermal energy 22. According to Reference Table I, the dissolving of NH4Cl(s) in water is 1) exothermic and the heat of reaction is negative 2) exothermic and the heat of reaction is positive 3) endothermic and the heat of reaction is negative 4) endothermic and the heat of reaction is positive 23. Which phase change is exothermic? 1) solid to liquid 2) solid to gas 3) liquid to solid 4) liquid to gas

5 Base your answers to questions 26 and 27 on the information below and on your knowledge of chemistry. A beaker contains a liquid sample of a molecular substance. Both the beaker and the liquid are at 194 K. The graph below represents the relationship between temperature and times as the beaker and its contents are cooled for 12 minutes in a refrigerated chamber. 26. State what happens to the average kinetic energy of the molecules in the sample during the first 3 minutes. 27. Identify the physical change occurring during the time interval, minute 4 to minute 9.

6 28. Base your answer to the following question on the information below. A student investigated heat transfer using a bottle of water. The student placed the bottle in a room at 20.5 C. The student measured the temperature of the water in the bottle at 7 a.m. and again at 3 p.m. The data from the investigation are shown in the table below. Show a numerical setup for calculating the change in the thermal energy of the water in the bottle from 7 a.m. to 3 p.m. 29. Base your answer to the following question on the information and diagram below, which represent the changes in potential energy that occur during the given reaction. Given the reaction: A + B C On the diagram provided draw a dashed line to indicate a potential energy curve for the reaction if a catalyst is added.

7 30. Base your answer to the following question on the information below. At a pressure of kilopascals and a temperature of 373 K, heat is removed from a sample of water vapor, causing the sample to change from time gaseous phase to time liquid phase. This phase change is represented by the equation below. H2O(g) H2O( ) + heat Determine the total amount of heat released by 5.00 grams of water vapor during this phase change.

8 Answer Key Energy The average kinetic energy decreases. The average KE goes down. 27. freezing, solidification, liquid to solid 28. q = (800. g)(4.18 J/g ºC)(20.5ºC 12.5ºC) (800)(4.18)(8) J