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 Extra ΔH QUESTIONS for Advanced Level Chemistry
Enthalpy Calculation Revision Questions for GCE-AS-A2-IB Advanced Level Chemistry 'HELP SCRIBBLES' * ANSWERS to the ∆H enthalpy Q's below * EMAIL Question 1 (a) Define the standard enthalpy of (i) combustion; (ii) formation (b) Given the following standard enthalpies of combustion (298K, 1 atmos.): C(s) -393 kJ mol-1; H2(g) -285.6 kJ mol-1; C2H6(g) -1560 kJ mol-1 (note: the first two enthalpies correspond to the enthalpy of formation of carbon dioxide and water respectively) Calculate the standard enthalpy of formation of ethane, C2H6(g) (c) Given the following bond enthalpies (bond energies) in kJ mol-1; C-H 412; C-C 347; O-H 464; O=O 498; C=O 805; C-O 358 calculate the enthalpy of combustion of ethane. (you will not get -1560 kJ mol-1, see later)
Question 2 Given the following standard enthalpies of combustion (298K, 1 atmos.): C(s) -393 kJ mol-1; H2(g) -285.6 kJ mol-1; C8H18(l) -5512 kJ mol-1; Calculate the enthalpy of formation of octane, C8H18(l)
Question 3 (a) Given the following standard enthalpies of combustion (298K, 1 atmos.): C(s) -393 kJ mol-1; H2(g) -285.6 kJ mol-1; and the enthalpy of formation of cyclohexane, C6H12(l) -156 kJ mol-1; Calculate the enthalpy of combustion of cyclohexane, C6H12(l) (b) Using the appropriate bond energies from Q1c calculate the theoretical enthalpy of combustion of cyclohexane.
(a) Given the following standard enthalpies of combustion (298K, 1 atmos.): C(s) -393 kJ mol-1; H2(g) -285.6 kJ mol-1; and the enthalpy of formation of ethanoic acid, CH3COOH(l) -487 kJ mol-1 Calculate the enthalpy of combustion of ethanoic acid, CH3COOH(l) (b) Using the bond enthalpies listed in Q1c calculate the enthalpy of combustion of ethanoic acid.
Question 5 Given the following standard Enthalpies of Formation (298K, 1 atmos.): NH3(g) -46.2 kJ mol-1; HCl(g) -92.3 kJ mol-1; NH4Cl(s) -315.0 kJ mol-1; Calculate the enthalpy change for the reaction: NH4Cl(s) ====> NH3(g) + HCl(g)
Question 6 Given the following standard Enthalpies of Formation in kJ mol-1 (298K, 1 atmos.): CH4(g) -74.9; CH3Br(l) -36.0; HBr(g) -36.2 Calculate the enthalpy change for the reaction: Br2(l) + CH4(g) ====> CH3Br(l) + HBr(g)
Question 7 (a) Define the term 'average bond enthalpy'. (b) Given the following standard Enthalpies of Formation in kJ mol-1 (298K, 1 atmos.): C3H8(g) -104 ; C3H7Cl(g) -105 ; HCl(g) -92 Calculate the enthalpy change for the reaction: Cl2(g) + C3H8(g) ====> C3H7Cl(g) + HCl(g)
(c) Given the following average bond energies in kJ mol-1: C-H 412 ; Cl-Cl 242 ; C-Cl 338 ; H-Cl 431 Calculate the enthalpy change for the same reaction as in (b). (d) Explain which of the calculations in (b) or (c) will be the most accurate and why?
Question 8 (a) Given the following standard Enthalpies of Formation in kJ mol-1 (298K, 1 atmos.): I2(g) +7.9 ; C2H6(g) -84.7 ; C2H5I(l) -31.0 ; HI(g) +25.9
Calculate the enthalpy change for the reaction: I2(g) + C2H6(g) ====> C2H5I(l) + HI(g)
(b) Given the following average bond energies in kJ mol-1: C-H 412 ; I-I 151 ; C-I 238 ; H-I 299 Calculate the enthalpy change for the same reaction in (a). (c) Suggest a reason why the calculations in (a) and (b) differ by a bigger % compared to similar calculations and data in Q's 1-4?
Question 9 Given the bond enthalpies in kJ mol-1: C-H 412, C-C 348 and H-H 436 (∆Hatom = 218 kJ mol-1). Calculate the enthalpy of formation of propane if the enthalpy of atomisation of carbon (graphite) is 715kJ mol-1. [ANSWERS to all of the questions above] Revision notes for studying revising tutoring teaching Advanced Level GCE AS A2 CHEMISTRY courses in unofficial support the Chemistry in any advanced-subsidiary AQA, Edexcel, OCR, CIE, WJEC, SQA and CCEA (NI) UK or Cambridge/London/Edexcel International and OCR/CIE and International Baccalaureate (IB) examinations as well as US grade 11-12 K12 courses. docbdfdhquestions June 15th 2008 * Copyright © Dr W P Brown 2000-2008 All rights reserved including the revision notes pages, quizzes, worksheets etc. * Doc Brown's Chemistry Clinic * www.docbrown.info/ * |
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GCSE-IGCSE-KS4 Science-CHEMISTRY notes & quizzes (~US K12 grades 9-10) |
Advanced Level CHEMISTRY GCE AS A2 IB notes and quizzes (~US K12 grades 11-12) |
All my GCSE-IGCSE Science-CHEMISTRY etc. syllabus help links |
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