Chemistry Past Papers Chapter 6

CHAPTER 6 1. Calculate the enthalpy value for: NO (g) + ½ O2 (g) → NO2 Using: ½ N2 + O2 (g) → NO (g) ΔHo = +90.37 kJ A) 56.57 kJ B) 124.17 kJ C) -56.57 kJ D) -124.17 kJ E) 213 kJ 2. CH4 (g) + 2O2 (g) → CO2 (g) + H2O (I) ΔH = -889.1 KJ ΔHfo H2O(I) = -285.8 kJ/mole ΔHfo CO2(g) =- 393.3 kJ/mole What is the standard heat of formation of methane ΔHfo CH4(g) in kJ/mol as calculated from the data above? A) -210 B) -107.5 C) -75.8 D) 75.8 E) 210 P a g e 36 | 45 3. Use the given standard enthalpies of formation to calculate the heat released per gram Fe2O3 (s). (molar mass of O = 16.00 and Fe = 55.85 g/mol). 3Fe2O3 (s) + CO (g) → 2Fe3O4 (S) + CO2 (g) A) -98.5 kJ/g B) 98.5 kJ/mol C) -101.9 J/g D) -98.5 J/g E) +101.9 J/g 4. For the following reaction: 2C (s) + 2H2O (g) → CH4 (g) + CO2 (g) ΔH= ? Use the following information to find ΔH: CO (g) + H2 (g) → C (s) + H2O (g) ΔH = -131 kJ CO (g) + H2O (g) → CO2 (g) + H2 (g) ΔH = -41 kJ CO (g) + 3H2 (g) → CH4 (g) + H2O (g) ΔH = -206 kJ A) -378 KJ B) 116KJ C) 15 KJ D) -116 KJ E) -372 KJ P a g e 37 | 45 5. Using the information below, calculate ΔHfo for PbO (s) in kJ/mol: PbO (s) + CO (g) → Pb (s) + CO (g) ΔHrxno = -131.4 kJ/mol Molecules ΔHfo (kJ/mol) CO(g) -110.5 CO2(g) -393.5 A) -413.9 kJ B) -151.6 kJ C) +372.1 kJ D) +413.9 kJ E) -372.1 kJ 6. When 3.50 g of sucrose undergoes combustion in a constant volume calorimeter, the temperature rises from 25.00oC to 29.00oC. Calculate ΔH for the combustion of sucrose in (KJ/mol) sucrose. The heat capacity of the calorimeter is 3.7 kJ/OC. (The molar mass of sucrose is 342.3 g/mol) C12H22O11 (s) + 12O2 (g) → 12CO2 (g) + 11H2O (I) A) -5.07 * 103 B) -1.45 * 103 C) +1.45 * 103 D) -1.48 * 103 E) +1.48 * 101 P a g e 38 | 45 7. When 500 ml of 0.400 M Ca(NO3)2 is added to 500 mL of 0.800 M NaF ,CaF2 precipitates, as shown in the net ionic equation below the initial temperature of both solutions is 20.00oC assuming that the resulting solution has a mass of 1000.00 g and a specific heat of 4.18 J/(g.oC). Calculate the final temperature of the solution. Ca2 (aq) + 2F - (aq) → CaF2 (s) ΔHo = -11.5 kJ A) 18.90oC B) 20.00 oC C) 19.45oC D) 20.55oC E) 21.10oC 8. What is the kinetic energy of mole of CO2 at 200 k (in kJ)? A) 200 KJ B) 4.14 * 10-2 KJ C) 2.5 * 10-2 KJ D) 0.200 KJ E) 2.49 KJ P a g e 39 | 45 9)Given the following data: ΔH(KJ) N2 (g) + 3/2 O2 (g) → N2O3 83.7 N2 (g) + O2 (g) → 2NO(g) 180.4 ½ N2 (g) + O2 (g) → NO2 (g) 33.2 Find H for this reaction: NO2 (g) + NO (g) → N2O3 A) -19.7 B) -59.7 C) 49.7 D) -29.7 E) -39.7 10. Given the following data: 2C6H6(I) + ΔHfo (KJ/mol): ? + 15O2(g) → 12CO2(g) + 6H2O(I) → -393.51 + -285.83 +49 Calculate the standard enthalpy of combustion of benzene in (kJ/mole benzene): A) -3135.5 B) 6535.2 C) -6270.9 D) -3267.6 E) -6535.2 P a g e 40 | 45 11. Given that ΔHfo for CO2 (g) = -393.5 kJ/mol. Which of the following thermochemical equations is correct? A) C (S, graphite) + O2 → CO2 (g) ΔHo = -393.5 B) C (S, graphite) + 2O → CO2 (g) ΔHo = -393.5 C) CO (g) + ½ O2 (g) → CO2 (g) ΔHo = -393.5 D) C (I) + O2 (g) → CO2 (g) ΔHo = -393.5 E) C (g) + O2 (g) → CO2 (g) ΔHo = -393.5 12. Consider the following thermochemical equations at 25oC: ClF (g) + ½ O2 (g) → ½ CL2O (g) + ½ F2O (g) ΔHo = +83.7 KJ Cl2O (g) + 3F2O (g) → 2ClF3 (g) + 2O2 (g) ΔHo = -341.4 kJ 2F2 (g) + O2 (g) → 2F2O (g) Δ Ho = -43.4 KJ Calculate ΔHo (in kJ) at 25oC for this reaction: CIF (g) + F2 (g) → CLF3 (g) A) -98.7 B) +142.7 C) -88.7 D) -108.7 E) -119.2 P a g e 41 | 45 13. When 27.6 mL of 0.870 M Lead (II) nitrate reacts with 90.0 mL of 0.777 M sodium chloride 0.297 KJ of heat is released at constant pressure what is ΔHo for this reaction? Pb(NO3)2 (aq) + 2NaCL (aq) → PbCL2 (s) + 2NaNO3 (aq) A) 11.6 kJ B) -69.7 kJ C) 69.7 kJ D) -11.6 kJ E) 17.4 kJ 14) Given the following data: Sublimation energy of Na = +108 kJ/mol First ionization energy of Na = +496 kJ/mol Electron affinity for Br = +325 kJ/mol Bond dissociation energy for Br2 = +196 kJ Calculate ΔHfo for the process (in kJ) for this reaction: Na+ (g) + Br (g) → NaBr (s) A) +562 B) -861 C) -735 D) -1253 E) +735 P a g e 42 | 45 15. What is the standard enthalpy of formation of liquid n-butanol CH3CH2CH2CH2OH? CH3CH2CH2CH2OH (I) + 6O2 (g) → 4CO2 (g) + 5H2O (I) ΔH = -2575 substance ΔHof (kJ/mol) H2O (I) -285.8 CO2 (g) -393.5 A) -528 kJ B) -428 kJ C) -328 kJ D) -753 kJ E) -603 kJ 16. Which of the following is not a state function? A) internal energy B) volume C) enthalpy D) pressure E) work P a g e 43 | 45 17. A system that does not work but which transfers heat to the system has: A) q < 0 and ΔU > 0 B) q > 0 and ΔU < 0 C) q > 0 and ΔU > 0 D) q < 0 and ΔU < 0 E) q < 0 and ΔU = 0 18. A gas is allowed to expand, at constant temperature from a volume of 4.0 L to 7.0 L against external pressure of 1.20 atm. If the gas absorbs 450 J of heat from the surrounding, then ΔE in J: A) -85 B) +207 C) -907 D) +85 E) -20 19. A system absorbs 25.8 kJ of heat while performing 10.9 kJ of work on the surroundings. If the final internal energy U is 70.8 kJ What is the initial value of U? A) 65.9 kJ B) 45.9 kJ C) 75.9 kJ D) 55.9 kJ E) 89.7 KJ P a g e 44 | 45 ‫‪20. Calculate ΔHo for the following reaction.‬‬ ‫)‪4NH3 (g) + 5O2 (g) → 4NO (g) + 6H2O (g‬‬ ‫‪ΔHoƒ NH3 (g) = -45.9 kJ/mol‬‬ ‫‪ΔHoƒ NO (g) = 90.3 kJ/mol‬‬ ‫‪ΔHoƒ H2O (g) = -241.8 kJ/mol‬‬ ‫‪A) 197.4 kJ‬‬ ‫‪B) -197.4 kJ‬‬ ‫‪C) -105.6 KJ‬‬ ‫‪D) -906.0 KJ‬‬ ‫‪E) 906.0 kJ‬‬ ‫بسم هللا الرحمن الرحيم‬ ‫َ ََ ُْ َ َ َ َْ‬ ‫َ ُ َ َّ‬ ‫ِّ ُ ُ‬ ‫ََ َ‬ ‫اْل ْرض َو َر َف َع َب ْع َض ُك ْم َف ْو َق َب ْ‬ ‫ات ل َي ْبل َوك ْم ِ يف َما‬ ‫ع‬ ‫ف‬ ‫ئ‬ ‫َل‬ ‫خ‬ ‫م‬ ‫ك‬ ‫ل‬ ‫ع‬ ‫ج‬ ‫ي‬ ‫ذ‬ ‫ال‬ ‫( وهو‬ ‫ِ‬ ‫ض درج ٍ‬ ‫ِ‬ ‫ٍ‬ ‫َ َّ ُ َ َ ُ‬ ‫َ ُ ْ َّ َ َّ َ َ ِ ُ ْ َ‬ ‫َّ‬ ‫ٌ‬ ‫ٌ‬ ‫اب و ِإنه لغفور ر ِحيم )‬ ‫آتاكم ۗ ِإن ربك ِ‬ ‫َسي ع ال ِعق ِ‬ ‫صدق هللا العظيم‬ ‫‪P a g e 45 | 45‬‬