This question paper consists of 5 pages each identified by the Code No. CHEM121001 May June 12 Š UNIVERSITY OF LEEDS School of Chemistry May/June 2012 CHEM121001 ENERGY MATTERS Time allowed: 2 hours Candidates should attempt all questions in Section A and all questions in Section B. Candidates are advised to spend no longer than 45 minutes attempting questions in Section A (40 marks). Questions in Section B are worth 20 marks each. Section A Answer all questions (Questions carry 5 marks each) 1. Briefly explain the following terms: wave-particle duality and Born interpretation of the wavefunction. 2. Use the formulae to explain why the wavefunctions of a particle in a one-dimensional box are not eigenfunctions of the momentum operator. 3. If a diatomic molecule vibrates harmonically, and the value of its zero-point energy is J, then what is the value of the gap between consecutive vibrational energy levels? 4. If the collisional cross-section for oxygen is 0.41 nm2, calculate the mean free path for oxygen stored in a cylinder at 20 bar and 212 K. 5. Draw a fully-labelled diagram to show how a nematic liquid crystal display works. 6. Explain, using a sketch of the phase diagram for CO2, what is meant by the critical point. Turn Over
CHEM121001 May/June 12 2 7. The base of a glass tube of internal radius 0.05 cm is placed in a bowl of hexane. Calculate how far up the tube the hexane will rise as a result of capillary action. The surface tension of hexane is 18.4 mN m-1 and its density is 0.65 g cm-3. You may find the formula below useful [g = 9.8 m s-2]. 8. On the same graph, draw the Maxwell distributions for the molecular speeds of He, N2 and CO2 at the same temperature; label each curve with the gas to which it corresponds. Turn Over
CHEM121001 May/June 12 3 Section B Answer all questions (Questions carry 20 marks each) 1. (a) A particle is set to move across a potential energy barrier. The figure below shows how the transmission coefficient changes with the…