This preview shows pages 1–2. Sign up to view the full content.
This preview has intentionally blurred sections. Sign up to view the full version.View Full Document
Unformatted text preview: Chem120B Problem Set 4 Due: February 22, 2008 1. Problems 18-37, and 18-39 in Simon and McQuarries Physical Chemistry . 2. Rotations about a covalent bond, such as the carbon-carbon bond in ethane, are hindered by forces between other chemical groups attached to the bonded atoms. The potential energy U due to these forces typically looks something like this: Your task is to sketch the heat capacity for this rotational degree of freedom as a function of tempera- ture. Here are some things to keep in mind: (a) When rotational energy is much less than the barriers sep- arating potential energy minima ( E ), the motion is oscillatory. In other words, it is like a harmonic degree of freedom. (b) When rotational energy is much greater than E , the motion is essentially unhindered. In other words, it is like a free rotation. (c) Imagine that the spacing between vibra- tional energy levels is small compared to E , so that the high-temperature limit of harmonic motion is reached before rotations become unhindered.is reached before rotations become unhindered....
View Full Document