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Molar Heat Capacity and Number of Degrees of Freedom

For vibrational motion a mole of molecules could

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Unformatted text preview: es of Freedom: Considering the equation given above for the total number of degrees of freedom, we can deduce that the number of degrees of freedom for vibration is given by: For linear molecules: #DOF(vibration) = 3N – 5 For non- linear molecules: #DOF(vibration) = 3N - 6 From Statistical Thermodynamics, we learn that for each degree of freedom (translational or rotational), a mole of molecules can absorb a thermal energy equal to ½ RT. For vibrational motion, a mole of molecules could absorb 2 x ½ RT = RT per degree of freedom, since vibrational motion has both kinetic and potential energy components. So, in principal a non- linear molecule with N atoms could exhibit the classical value of the molar heat capacity at constant volume given by: CVm = 3/2 R + 3/2 R + (3N...
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