AlGore - Natural CO2 is heavier than man-made CO2. Is this true?

[rrr51]

I was listening to the hearings and just heard AlGore say that natural CO2, such as CO2 produced by volcanos, is heavier than CO2 produced by man. Did I hear right? Is that what he said? Is it true? Does anybody know?

[patton]

Now, Robert, don't confuse the discussion, by bringing up abiotic oil...LOL

[edsheppa]

how much CO2 comes from non-biologic sources?

Sorry, I don't know.

[tioga]

I am sooo relieved that you cleared that up for me....the divinity school flunkie had me scared.

[spunkets]

It's not really chemistry, it's physics. Each element gets it's identity from the number of protons. The number of neutrons can vary. The neutrons stabilize the nucleus, because the protons and neutrons exchange identities - they convert into each other. The strong force is what's involved. That force holds the nucleus together, against the electromagnetic force of the protons repelling each other. The conversion involves the exchange of a particle called a π meson, the pion, which is the carrier of the strong force. All elements above hydrogen need neutrons to stabilize the nucleus.

For any particular element, there is more than one stable isotope, so the number of neutrons can vary. Stable just means that the decay is on the order of the age of the universe, near it. The assemblies of protons and neutrons themselves are lower, and higher energy configurations. The iron nucleus has the lowest energy configuration. Elements below iron fuse to approach iron, and those of higher atomic weight split.

For carbon, both ¹²C and ¹³C are stable. ¹⁴C is not, and has a half life of ~5700yrs. In chemical bonding, the weight of the nuclei are important. They effect the value of the reduced mass of the nuclear/electron system, and the nuclear/nuclear system. In a 2 body system, both masses move about the center of mass. In order to solve and simplify the problem, the 2 body problem is transformed into a problem consisting of one infinite mass at the center of mass, and another reduced mass, that is movable. For a one electron atom, the energy levels of the electron are directly proportional to the reduced mass, so as the nuclear mass increases, the magnitude of the energy level of the electron increases.

Since the electron is bound, the sign of the energy is negative. So, as the mass of the nucleus increases, the electron falls into a deeper well. It is bound tighter. The ionization energy for deuterium, ²H, or D, is ~0.1% higher than for regular hydrogen, ¹H. So, the spectrum of D is shifted to shorter wavelengths s bit, and tritium, ³, even more so. That's because the reduced mass of the electron increases.

For bonding of 2 atoms, the nuclear motion, and the electronic motions can be separated. That's called the Born-Oppenheimer approximation. The above holds for the electronic motion, and the energy of the electrons involved in the binding is more negative, as the mass of the nuclei increases. The nuclear motions follow the same, as the mass increases, the 2 are effectively bound tighter. Their vibrational frequencies are lower, which means the well is deeper, and their ground states, or zero point energies are lower. That doesn't mean "the spring" binding them has a higher force constant. It just means "the spring" is harder to break.

The spring is still the electromagnetic force. What makes the spring harder to break, or a stronger bond, is that the mass of the nucleus moves less. In molecular binding the electrons involved in the bonding will be in more stabilizing trajectories than is possible if the nuclei move in a greater range of motion. The stability of the system is really the result of summing all the possible trajectories of the electrons involved, and minimizing the total energy. If the nuclear masses move to a smaller extent, their are less high energy possibilities. Also, when more than one electron is involved in the binding, the electrons "correlate" their motion to lower electron-electron repulsion. When the nuclear mass increases, there are less high energy correlations for the same nuclear charges. ...they're less probable.

So, D in D₂2. As the element's atomic number increases, the effect of nuclear mass decreases, because the percentage increase in mass decreases. So as ¹³C is 8% heavier than ¹²C, the binding energy is greater. That means compounds involving ¹²C will react easier than those involving ¹³C. So in any system involving these reactions, ¹²C will concentrate in the products, and more ¹³C will be left as reactant. As the elements mass increases, this fractionation effect becomes smaller. That's why uranium isotopes, are separated by physical means in a great number of steps.

Here's an example of fractionation of isotopes through another physical process for oxygen. In this case it's the increase in E needed to vaporize the higher mass isotope, that results in separation. Note gravity is irrelevant. It's the inertial mass that needs more E to move it out of a bound position that's important.

[varon]

AlGore - Natural CO2 is heavier than man-made CO2. Is this true?

Of course it's true, just like everyone knows that a pound of lead is heavier than a pound of feathers ;-)

[spunkets]

" So, D in D₂2"

Sorry, that should have read:

So, D in D₂ is ~1.3% lower in energy than H in H₂. The D₂ bond is ~1.3% harder to break, or a ~1.3% stronger bond.

[doug from upland]

I didn't take physics. Thanks for the explanation. I'll keep reading it and trying to understand it. :)

[spunkets]

You're welcome. Basically heavier things take more energy to move. When the energy is the same, they don't move as far as a smaller mass, so the system is more stable. Even if the mass is close, the effect is still there.

I left a mistake in there from typing fast. The ionization energy of a D atom is ~0.03% greater than an H atom, not ~0.3%.

[spunkets]

"There is a minute difference between C12 and C14, and the two have slightly different ratios in wood (plant life) and atmospheric ratios, but :fossil fuel" IS plant life-derived (so we are told by classic chemistry!) but that has no difference in the emissions of burning old plant life or new plant life ... "

The isotope that's important is the stable isotope ¹³C. ¹²C is preferentially incorporated into vegitation, because the ¹³C/oxygen bond is slightly stronger, than the ¹²C/O bond. That results in an increased isotopic ratio of ¹³C/¹²C in the atmosphere, over the general natural abundance ratio. See #284. There's some corrections in 2 posts below it, a missing H for ³H...

" UNLESS you consider petroleum based oils are NOT from "plant-life" derivatives, in which case they come from ?"

¹⁴C would be irrelevant in this case, because the oil is millions of years old, and the half life of ¹⁴C i ~5700yrs.

[spunkets]

"What effect does the extra mass of C14 have on the vibroational spectrum of CO2? Too lazy to track down a copy of Herzberg..."

See #284, there's some corrections in posts below it. The vib freq drops as the reduced mass goes up. The well for the bound particles also gets deeper as the mass increases. The force constant stays the same, because it's the same electrostatics. The bond is just harder to break, because it takes more energy to move a higher mass.

[grey_whiskers]

Everything you said is true: but apparently the problem with CO₂ is that the rotational spectrum is what makes it important to global warming--and the absorption bands pretty much overlap some important bands for water, making a trivial measurement difficult.

The change in vibrational frequencies would have an effect on the rotational spectrum as a 2nd order effect through the coupling of vibration and rotation.

All the same, I appreciate your taking the time to answer courteously, even if it didn't turn out to be what I was so haughtily demanding ;-)

Cheers!

[spunkets]

"pparently the problem with CO2 is that the rotational spectrum is what makes it important to global warming--and the absorption bands pretty much overlap some important bands for water, making a trivial measurement difficult."

It's the vib-rottional spectrum that results in the energy absorbtion. They are coupled. Yes, water is the major greehouse gas, and CO₂ only amounts to a small percentage. The isotope effect here is negligable. Isotopes are just used to measure flux of CO_{2 into and from various sources and sinks.}

"The change in vibrational frequencies would have an effect on the rotational spectrum as a 2nd order effect through the coupling of vibration and rotation."

A vibrational transition must be accompanied by a rotational tranisition. It's a moment of inertia change. So, each vib band is broadened on both sides of a non-appearing center frequency. There's also transitional energy, which amounts to doppler broadening. The isotope effect is buried in there, so assuming it's all one isotope is good enough. Any ¹³C, or ¹⁴C effectively just increases the conc of ¹²C.

[doc30]

It will slightly lower the fundamental bands. But when you are talking about long path length gas phase spectroscopy, with very fine bands, such a shift will place absorbaces in regions C12 doesn't absorb. This is all around 500 cm-1 or so (black body at 20'C, or so).

[grey_whiskers]

(Tips hat)

Thanks, exactly what I was looking for.

Cheers!

[beebuster2000]

sorry guys. man made CO2 is heavier than natural. here is why the majority of man made CO2 originates in human activity like suv driving and coal power plants which tends to create the CO2 in denser quantities than the natural process of plant decomposition, etc. Because of the density, the man made CO2 triggers the electron level valence carbon atom affinity effect which tends to clump the CO2 until it reaches the critical quantum dense pack inter-molecular stage at which point the valence affinity is overidden and the dense-pack effect endures for some time. by the way, the Nobel prize for chemistry in 1954 was awarded for the discovery of this phenomenom. Please do your research before posting.

[grey_whiskers]

I'm speechless.

[beebuster2000]

small wonder. I stayed at a Holiday Inn last night so this was pretty trivial.

[chinche]

Denser CO2 than what would come from a forest fire, a volcano, etc.?

[beebuster2000]

yes, much denser. see my post above for explanation.

denser at point of creation but also the effect intensifies with time. its just simple chemistry

[Covenantor]

Please explain the mechanism by which carbon dioxide, in any form, causes atmosphereic warming or retention of heat. I have yet to read a comprehensive description of this.

It mystifies me that an odorless, colorless gas that constitutes a mere 0.04 % (approx.) of the earth's atmosphere has these magical properties.