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Thermal & Kinetic Lecture 10 Revision I: Problems and Previous Exam. Questions

Thermal & Kinetic Lecture 10 Revision I: Problems and Previous Exam. Questions. I would prefer to have the slides available from the website before the lecture. Yes No Don’t care. Equipartition and Specific Heats. Thermal & Kinetic paper, ’06/’07: Q1. For this question,.

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Thermal & Kinetic Lecture 10 Revision I: Problems and Previous Exam. Questions

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  1. Thermal & Kinetic Lecture 10 Revision I: Problems and Previous Exam. Questions

  2. I would prefer to have the slides available from the website before the lecture. • Yes • No • Don’t care

  3. Equipartition and Specific Heats

  4. Thermal & Kinetic paper, ’06/’07: Q1

  5. For this question, • I don’t know where to begin • I could have a go but I’m not sure • I am confident that I can do it

  6. The value of CV expected if all degrees of freedom contribute is: • 24.93 JK-1 • 12.46 JK-1 • 29.08 JK-1 • None of these

  7. Thermal & Kinetic paper, ’02/’03: Paper 2, Q1

  8. Vibrational effects… • Won’t contribute • Will contribute • Don’t know

  9. (b) (i)kT at room temperature ~ 0.025 eV. Spacing of vibrational levels ~ 1 order of magnitude greater than this – vibrational contribution will be negligible.

  10. At what temperature will the population of the first excited vibrational level be a factor of ten greater than the number of molecules in the second vibrational level? • 512 K • 1361 K • 77 K • 2112 K

  11. (b) (ii) ln (10)=0.27 x 1.6 x 10-19/(1.38 x 10-23 x T) [1]  T = 1361 K [1] (b)(iii)Consider independent degrees of freedom of diatomic molecule: 3 translation, 2 vibration, 2 rotation [1]. Each degree of freedom contributes ½ kT in energy, hence Cv = 7k/ 2 (7R/2 for 1 mole) [1] Only have 3 degrees of freedom for monatomic gas, so Cv = 3k/2 (3R/2 for 1 mole) [1]

  12. Thermal & Kinetic paper, ’05/’06: Q3

  13. For this question, • I don’t know where to begin • I could have a go but I’m not sure • I am confident that I can do it

  14. Specific heats and equipartition of energy If the spacing of the rotational energy levels for a certain diatomic molecule is 0.05 eV, would you expect that rotational effects will make a strong contribution to the specific heat of the molecule at a temperature of 4K? What is the heat capacity of the molecule at 4K assuming that both vibrational and rotational motion are ‘frozen out’ at this temperature?

  15. Thermal & Kinetic paper, ’03/’04: Section B Q8 NB You should attempt the remainder of Q8 from the 2004 Thermal & Kinetic paper.

  16. Boltzmann distribution

  17. Thermal & Kinetic paper, ’06/’07: Paper 2, Q1

  18. The dimensions of k are: • MLT-2q • ML2T-1q2 • ML2T-2q-1 • Don’t know

  19. Velocity and speed (Maxwell-Boltzmann) distributions

  20. Thermal & Kinetic paper, ’04/’05: Section B Q7 Formulae given

  21. For this question, • I don’t know where to begin • I could have a go but I’m not sure • I am confident that I can do it

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