CAS CH 112 Lecture Notes - Lecture 4: Rotational Energy, Heat Capacity
24 Mar 2019
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Document Summary
R joules of thermal energy are stored per vibrational mode: higher energy is due to kbt in the kinetic energy of the atomic motion and kbt in the potential energy of the bonds. Number of vibrational df: dfvib= 3n dftrans dfrot where n= # of atoms, ex: diatomic linear molecule 3(2) 3 2 = 1 vibrational df and a maximum cv= 3 r. Nonrigid molecules and solids kinetic energy is stored in oscillations which gives a maximum heat capacity as 3r per atom. Heavier atoms and large molecules make vibrational modes more accessible [e= n2h2/8ml2] Solids always have maximum of 3r for cv, but they actually vary between 0 and 3r with increased temperature.
