Download Mass Percentage Composition - Physical Chemistry - Exam and more Exams Physical Chemistry in PDF only on Docsity! 1 of 5 Semester I Examinations 2010/ 2011 Exam Code(s) CHEMISTRY CH203 Exam(s) Second Year Physical Chemistry Module Code(s) CH203 Module(s) PHYSICAL CHEMISTRY Paper No. 1 Repeat Paper External Examiner(s) Prof. Paul Seakins Internal Examiner(s) Prof. P. Murphy, Dr. W. M. Carroll, Dr. H. Curran, Dr. D. Leech, Dr. A. Ryder Instructions: ANSWER FOUR (4) QUESTIONS, ONE FROM EACH SECTION Duration Two (2) Hours No. of Pages 5 Department(s) Chemistry Course Co-ordinator(s) Dr. D. LEECH Requirements: MCQ Release to Library: Yes X No Statistical/ Log Tables x Graph Paper x Gas constant, R = 8.3143 J K–1 mol–1 Avogadro constant, NA = 6.022 × 1023 mol–1 Planck constant, h = 6.624 × 10–34 J s Velocity of light, c = 2.998 × 108 m s–1 Electronic charge, e = 1.602 × 10–19 C Boltzmann constant, k = 1.381 × 10–23 J K–1 Electronic mass, m = 9.109 × 10–31 kg Bohr magneton, µB = 9.274 × 10–24 J T–1 Faraday constant, F = 96,485 C mol–1 1 atm = 101,325 N m–2 = 101,325 Pa 2 of 5 Section A: Attempt one question from this Section (gases and thermodynamic laws) 1. Answer (a), (b) and (c). (a) The mass percentage composition of dry air at sea level is approximately 75.52 N2 (molar mass 28.01 g mol-1), 23.15 O2 (molar mass 32.0 g mol-1), 1.28 Ar (atomic mass 39.95 g mol-) and 0.046 CO2 (molar mass 44.01 g mol-1). What are the partial pressures when the total pressure is 100 kPa? [8 marks] (b) Define the compression factor and explain how it varies as a function of pressure and temperature. Describe how the compression factor reveals information about intermolecular interactions in real gases. [12 marks] (c) Define all of the terms in Graham’s law of effusion, below, and use the law to estimate the relative rate of effusion of hydrogen (molar mass 2.016 g mol-1) and carbon dioxide (molar mass 44.01 g mol-1) under the same conditions of temperature and pressure. [5 marks] 2. Answer (a) and (b). (a) In an experiment to measure the heat released by combustion of a sample of nutrient, the compound was burned in a calorimeter and the temperature rose by 2.98°C. When a current of 1.18 A from a 12 V source flows through a heater in the same calorimeter for 120 s, the temperature rose by 4.37°C. What is the heat released by the combustion reaction? [8 marks] (b) Given that the work, w, required to move an object a distance, l, against an opposing force, F, is −F.dl, derive the expression below for the work of isothermal reversible expansion of an ideal gas. Estimate the work, heat and entropy change for the isothermal reversible expansion of 1.0 mol of an ideal gas at 273 K from 1 L to 2 L volume, commenting on the values obtained. i f V V nRTw ln−= [17 marks] 1 2 2 1 M M r r =
