Second Year Chemistry Exam: Physical Chemistry (CH203), Exams of Physical Chemistry

Download Second Year Chemistry Exam: Physical Chemistry (CH203) and more Exams Physical Chemistry in PDF only on Docsity! Page 1 of 5 Ollscoil na hÉireann, Gaillimh National University of Ireland, Galway Autumn Examination 2009 Second Year Chemistry Physical Chemistry (CH203) All questions carry equal marks, distributed as shown Answer four (4) questions One (1) from each Section Time allowed: two (2) hours Professor Paul D. I. Fletcher Professor Paul V. Murphy Dr William Carroll Dr Henry Curran Dr Dónal Leech Dr Alan Ryder Gas constant, R = 8.3143 J K–1 mol–1 Avogadro constant, NA = 6.022 × 10 23 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 atmosphere = 101,325 N m–2 Page 2 of 5 Section A: Attempt one question from this Section (gases and thermodynamic laws) 1. Answer (a), (b) and (c). (a) If dry air is composed of N2, O2 and Ar at sea level in mass percent of 75.5: 23.2: 1.3. What is partial pressure for each component when the total pressure is 1.0 bar? [9 marks] (b) Describe the formulation of the van der Waals equation from the ideal gas law, defining each term in the equation. [9 marks] (c) An aerosol spray can with a volume of 150 cm 3 contains 3.5 g of propane (C3H8) as a propellant. If the can is at 18 o C what is the pressure in the can? The can says that exposure to temperatures above 55 o C may cause the can to burst. What is the pressure in the can at this temperature? [7 marks] 2. 1.5 mol of an ideal gas at 273 K is expanded reversibly and isothermally from 10 bar to 1 bar pressure. Calculate q, w, ∆U, ∆H and ∆S for the process. Explain the significance of each of these variables. [25 marks] 2       − − = V n a nbV nRT P