Thermodynamics Unit Test AP Chemistry Address 23 out of 25 Period:

Transcription

1 Thermodynamics Unit Test Name: AP Chemistry Address 23 out of 25 Period: 1. Based on the above table what is the H for the reaction below? 2 CH2O2(g) + O2(g) 2 CO2(g) + 2 H2O(g) A) 128 kcal B) +128 kcal C) 238 kcal D) +238 kcal E) 64 kcal 2. Which of the following reactions have positive entropy? I. 2 NO(g) + O2(g) N2O4(g) II. 2 C6H6(l) + 15O2(g) 12 CO2(g) + 6 H2O(l) III. 3 C(s) + 3 O2(s) 3 CO2(g) A) I only B) II only C) III only D) I and II only 3. Which of the following reactions has the largest increase in entropy? A) 2 La2O3(s) 3 O2(g) + 4 La(s) B) Cu 2+ (aq) + 2 Ag + (aq) Cu 2+ (aq) + 2 Ag(aq) C) H2(g) + 2 KOH(aq) H2O(l) + 2 K(s) D) 2 CO(g) + O2(g) 2 CO2(g) E) Pb(NO3)2(s) + 2 KI(s) PbI2(s) + 2 KNO3(s) 4. Which has an unfavorable entropy change, DS? 5. When a certain salt is dissolved into water, it raises the temperature of the water. Which of the following is true? H S A) Negative Positive B) Negative Negative C) Negative 0 D) Positive Positive E) Positive Negative 6. Which condition must hold true at equilibrium? 7. A) DH < 0 B) DH = 0 C) DG < 0 D) DG = 0 E) DS = 0 A) I B) II C) III D) IV E) All have a favorable entropy change According to the table above, which reactions occur spontaneously? A) II and IV B) II and III C) I and III D) I and IV E) I and II 8. If DG o < 0 and Keq > 1, then which statement must be true for a reaction starting in standard state conditions? A) The reaction will proceed rapidly. B) The rate of reaction cannot be determined. C) The reaction will not be spontaneous. D) The reaction will proceed spontaneously. E) Spontaneity will depend on the temperature of the system. Page 1

2 9. Heat of Vaporization of Ethanol, CH3CH2OH = 880. J g Given the potential energy diagram: How many Joules are needed to vaporize 2.00 g of liquid ethanol, CH3CH2OH, at its boiling point, 78 C? A) 557 J B) 673 J C) 880 J D) 1760 J E) 3360 J 10. Given the balanced equation: I2(s) + energy I2(g) As a sample of I2(s) sublimes to I2(g), the entropy of the sample A) increases because the particles are less randomly B) increases because the particles are more randomly C) decreases because the particles are less randomly D) decreases because the particles are more randomly 11. Systems in nature tend to undergo changes toward A) lower energy and lower entropy B) lower energy and higher entropy C) higher energy and lower entropy D) higher energy and higher entropy 12. 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 A) 8.0 C B) 14 C C) 30. C D) 55 C 13. What is the total number of kilojoules of heat energy absorbed when the temperature of 200 grams of water is raised from 10ºC to 40ºC? A) kj B) kj C) 25.2 kj D) 33.6 kj 14. Base your answer to the following question on In an experiment using a calorimeter, the following data were obtained: With reference to energy, the reaction A + B best be described as A) endothermic, having a + H B) endothermic, having a H C) exothermic, having a + H D) exothermic, having a H AB can 16. When a spark is applied to a mixture of hydrogen and oxygen, the gases react explosively. Which potential energy diagram best represents the reaction? A) B) C) D) What is the total number of Joules absorbed by the water? A) 4200 B) 6300 C) D) Page 2

3 17. Base your answer to the following question on the potential energy diagram below, which represents the reaction: A + B C + energy. 18. Which statement correctly describes this reaction? A) It is endothermic and energy is absorbed. B) It is endothermic and energy is released. C) It is exothermic and energy is absorbed. D) It is exothermic and energy is released. Based on the table above, what is the DHº for the reaction N2O4 + O2 N2O5? A) 67.0 J B) 14.8 J C) 1.30 J D) J E) J 19. Based on the table below, what is the free energy change for the reaction C2H4(g) + 3 O2(g) 2 H2O(g) + 2 CO2(g)? A) +282 kcal B) 282 kcal C) 104 kcal D) +104 kcal E) 408 kcal Page 3

4 20. If G of a reaction is positive at 300 K, which of the following must be true? I. The reaction does not occur spontaneously at 300 K. II. The reaction is endothermic. III. The reverse reaction has a negative G A) I only B) III only C) I and II only D) I and III only Base your answers to questions 21 and 22 on the reaction below. 21. Which statement is the most accurate regarding this reaction. A) It is spontaneous and exothermic. B) It is spontaneous and endothermic. C) It is non-spontaneous and exothermic. D) It is non-spontaneous and results in an increase in entropy. E) It is non-spontaneous and results in an decrease in entropy. 22. If the rate expression for this reaction does not depend on B, what could be the cause of this? A) B is not involved in any steps in this reaction. B) B is not involved in the rate determining step, but may be involved in other steps in the reaction. C) The coefficient of B is 1, therefore it does not affect the rate of the reaction. D) B is a solid, therefore does not appear in the rate expression. E) The order of the reaction with respect to B is The following endothermic reaction occurs in a rigid container. 2 SO3(g) «2 S(s) + 3 O2(g) Which of the following causes more oxygen to be produced? I. Increase in pressure. II. Increase in temperature. III. Introduction of a catalyst. A) I only B) II only C) III only D) I and II only 24. Cl2(g) + 3 O2(g) «2 ClO3(g) kj/mol 25. In the above equation, which of the following will result in a shift to the LEFT? A) Increasing the pressure on the system B) Adding heat energy to the reaction C) Decreasing the volume of the system D) Removing ClO3 from the system E) Adding Cl2 to the reaction Cgraphite + 2 Cl2(g) CCl4 Hfº = 107 kj mol 1 Based on the above table and equation, what is the bond energy of the C-Cl bond? A) 240 kj mol 1 B) 1308 kj mol 1 C) 327 kj mol 1 D) kj mol 1 E) 266 kj mol 1 Page 4

5 Answer Key Thermodynamics 1. A 2. C 3. A 4. B 5. A 6. D 7. E 8. D 9. D 10. B 11. B 12. C 13. C 14. B 15. D 16. B 17. D 18. D 19. B 20. D 21. A 22. B 23. B 24. B 25. C Page 5