Thermodynamics Review 2014 Worth 10% of Exam Score

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1 Thermodynamics Review 2014 Worth 10% of Exam Score Name: Period: 1. Base your answer to the following question on the diagram shown below. 4. The heat of combustion for is kcal. What is the heat of formation for? A) B) C) D) E) kcal kcal kcal kcal kcal Which represents the heat of reaction? A) 1 B) 2 C) 3 D) 4 E) 5 2. CuO + H2 Cu + H2O(l) DH= kj What is the value of DH if the reaction produced water vapor instead of liquid water? (DH = 44 kj/mol for the phase change H2O(l) H2O(g)) A) 86.6 kj B) kj C) kj D) kj E) 42.6 kj 3. Which of the following graphs represents an exothermic reaction with a low activation energy? A) B) C) D) Page 1

2 5. 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 O2(g) + H2(g) H2O(g) kj 12 O2(g) + 2 H(g) H2O(g) kj Given the above two equations, how much energy is needed to dissociate 1.00 mole of H2 according to the equation below? 9. H2(g) 2H(g) A) 243 kj B) 418 kj C) 661. kj D) 904. kj E) 1320 kj Based on the above bond energies, what is the heat of reaction for the reaction: 7. 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? 10. A) B) C) D) E) A) 240 kj mol 1 B) 1308 kj mol 1 C) 327 kj mol 1 D) kj mol 1 E) 266 kj mol 1 8. The combustion of methane has a heat of reaction of 891 kj per mole. It results in gaseous carbon dioxide and liquid water. If the reaction produced gaseous water instead of liquid water, what would the heat of reaction be? ( H for H2O(g) H2O(l) is 44kJ/mol ) A) 803 kj/mol B) 847 kj/mol C) 891 kj/mol D) 935 kj/mol E) 979 kj/mol Use the values of the standard heat of formation in the above table to calculate the heat of reaction, DH, for the reaction A) kj B) 265 kj C) +2,240 kj D) -13,400 kj E) -265 kj Page 2

3 11. 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 12. When 4.4 g of NH4CN dissolves in 100. g water at 20.ºC the temperature rises to 24.2ºC. What is the value of the enthalpy change of solution, DHsolution of NH4 CN? A) kcal B) 4.2 kcal C) 0.42 kcal D) kcal E) +9.7 kcal 13. 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 E) I, II, and III 14. 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) 15. Which has an unfavorable entropy change, DS? A) I B) II C) III D) IV E) All have a favorable entropy change 16. Which forward reaction below indicates an entropy decrease? A) C6H6(s) «C6H6(l) B) 2 IBr(g) «I2(s) + Br2(l) C) NH4Cl(s) «NH3(g) + HCl(g) D) (NH4)2CO3(s) «2 NH3(g) + H2O(g) + CO2(g) E) H2O(s) «H2O(g) 17. Which of the following reactions would you expect to have a negative DS? A) I2(g) I2(s) B) 2 NH3(g) 3 H2(g) + N2(g) C) BaO2(s) 2 Ba(s) + O2(g) D) CaCO3(s) CaO(s) + CO2(g) E) 2 HBr(g) H2(g) + Br2(g) 18. The heat of fusion of Aluminum bromide is 21.6 kj mol 1. The entropy change of fusion is 60.0 J K 1 mol 1. What is its normal boiling point. A) 360.ºC B) 87.0ºC C) 8.70ºC D) 3.60ºC E) 0.870ºC 19. When the temperature change of a system is low, the reaction generally proceeds as predicted by the enthalpy change (DH) because A) DS is negative B) the product TDS is equal to DH C) the product TDS is small compared to DH D) the product TDS is large compared to DH E) the product TDS cannot be determined compared to DH Page 3

4 20. 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 21. Which condition must hold true at equilibrium? 22. A) DH < 0 B) DH = 0 C) DG < 0 D) DG = 0 E) DS = 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 The data above represents the standard entropy and free energy of four compounds formed from their respective elements at 298 K and 1.0 atm pressure. For which of the four compounds will a temperature increase change the reaction from being nonspontaneous to spontaneous? A) A B) B C) C D) D E) All reactions will change from nonspontaneous to spontanteous 24. Which of the following reactions would be spontaneous at 1000 K? A) DH = + 50 kj DS = 50 J B) DH = +50 kj DS = 50 J C) DH = 70 kj DS = 60 J D) DH = + 0 kj DS = 0 J E) DH = 10 kj DS = 10 J Page 4

5 25. 4 HCl(g) + O2(g) 2 Cl2(g) + 2 H2O(g) The above reaction is not spontaneous at 700 K but is at lower temperatures. Which of the following describes the reaction at 700 K? A) DG, DH, and DS are positive B) DG, DH, and DS are negative C) DG and DS are negative; DH is positive D) DG and DH are negative; DS is positive E) DG and DS are positive; DH is negative 26. Base your answer to the following question on the reaction below. 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. Page 5