Molecular Vibration and Translational Kinetic Energy in a Gas

In summary, CO2 molecules have absorption peaks at 2.7, 4.3, and 15 microns and become vibrationally excited. When re-emitting energy, they do not necessarily emit at the same wavelengths as their absorption spectrum and do not behave like a blackbody. In a gas, vibrational energy can be transferred to other molecules through collisions, but it can also be emitted as radiation. It is possible for vibrationally excited CO2 molecules to do work on other molecules in the gas, not just on other CO2 molecules. The gas in question is air, not an ideal gas.
  • #1
Wilko
11
0
I understand that CO2 molecules absorb infrared at 2.7, 4.3 and 15 microns, this makes them become vibrationally excited (rocking, stretching, bending, I don't know all the modes).

I have a few questions from this point:

1. When the CO2 molecule re-emits that energy is it obliged to do so at wavelengths similar to its absorption spectrum; I had assumed so but I don't know for certain that this is the case despite googling the hell out of it. CO2 does not behave in anyway like a blackbody when it re-radiates, correct?

2. In a gas, can the vibrational energy be passed from the CO2 molecule to other molecules during collisions, or can it only pass on as radiation? I understand there's a lattice effect in solids, but I don't think its relevant in a gas. Can molecular vibration 'turn into' translational kinetic energy?

3. Assuming that the CO2 molecule re-radiates at 2.7, 4.3 and 15 microns, I imagine that H20 may 'feel' that radiation at 4.3 microns, but I guess what I'm really asking is, can vibrationally excited CO2 molecules, do work on the rest of the molecules in the gas? Or is the vibrational energy of a CO2 molecule limited to doing work on other CO2 molecules?
 
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  • #2
Sorry, I should have added, the gas isn't an ideal gas, it's air!
 
  • #3
Have I framed my question incorrectly? Or gravely misunderstood something?
 

FAQ: Molecular Vibration and Translational Kinetic Energy in a Gas

1. What is molecular vibration in a gas?

Molecular vibration refers to the movement of molecules within a gas. These movements involve the stretching and bending of the chemical bonds between atoms, which creates a change in the overall energy of the molecule.

2. How does molecular vibration affect the properties of a gas?

Molecular vibration affects the properties of a gas by influencing its temperature, pressure, and volume. As molecules vibrate, they gain kinetic energy, which increases the temperature and pressure of the gas. Additionally, the movements of molecules also contribute to the volume of the gas as they take up space.

3. What is translational kinetic energy in a gas?

Translational kinetic energy is the energy associated with the movement of gas molecules in a particular direction. This type of kinetic energy is a result of the random and constant motion of gas molecules, which is influenced by factors such as temperature and pressure.

4. How does translational kinetic energy affect the behavior of a gas?

Translational kinetic energy is directly related to the temperature and pressure of a gas. As the temperature increases, the translational kinetic energy of the gas molecules also increases, resulting in a greater speed and more frequent collisions between molecules. This leads to an increase in pressure and a decrease in volume. Similarly, a decrease in temperature results in a decrease in translational kinetic energy, leading to a decrease in pressure and an increase in volume.

5. What is the relationship between molecular vibration and translational kinetic energy in a gas?

Molecular vibration and translational kinetic energy are both forms of kinetic energy that contribute to the overall behavior of a gas. Molecular vibration refers to the internal movement of molecules, while translational kinetic energy refers to the external movement of molecules. These two forms of energy are interrelated, as the movement of molecules within a gas affects their overall speed and kinetic energy, which in turn affects the temperature, pressure, and volume of the gas.

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