While everyone is worried about CO2 levels, what about CO levels in the atmosphere? It is widely known that CO is an unavoidable waste product of combustion. So, after all the ages of burning things, why hasn’t the CO levels asphyxiated all of Mankind by now? Does CO readily decompose in sunlight/UV?
Wikipedia had this factoid:
I assumed that CO isn’t very stable, but apparently I was very wrong on that. (It has a triple bond… how is that even possible?)
Also:
I suspect that CO is only formed in low quantities (such powerful bonds probably don’t form easily).
It’s quite flammable in its own right, so perhaps a lot of it is consumed as quickly as it’s produced. It’s also lighter than air, so there’s probably a fair amount lost to space.
CO is lighter than air and so rises. So outside it rises and doesn’t really do much at all.
The build up in enclosed areas is where it is very dangerous.
CO is not really a Greenhouse gas as it only absorbs a little heat for the sun, but it does play into methane production. Sorry, but the science here is outside of my comfort zone and I’ll probably get it wrong.
There is a problem in large dense cities with CO buildup, this is the reason for the many localities discouraging and/or ticketing idling cars. Again, the science is outside my comfort zone.
As of 2012, this is not very well understood. We know that CO levels decline over time in the upper and lower atmosphere but how exactly is not well understood.
Link : https://www.tandfonline.com/doi/abs/10.1080/00022470.1968.10469168
Are you the inventor of time travel, or are you using someone else’s machine?
The quantity formed depends on the circumstances of the reactions involved. If you’re running an engine lean or stoichiometric, you won’t get much CO. If you’re running it rich, you’ll generate lots. Here’s a chart showing what comes out of a gasoline engine at various air/fuel ratios. The stoichiometric blend is about 14.7:1, and as you go rich from there, you can get CO output as high as 5%. On a late-model vehicle with a fully warmed-up engine, the A/F ratio is generally maintained very close to stoichiometric, resulting in engine-out CO levels of less than 1%, after which the exhaust aftertreatment system catalyzes almost all of it, getting it down to PPM levels.
Although the high dissociation energy you cited is an obstacle to quick oxidation of CO into CO2 at atmospheric conditions, the significant heating value of CO leads me to suspect that the room-temperature equilibrium concentration of CO is extremely low - which means that, given enough time, CO molecules that are present in any significant concentration will tend to spontaneously oxidize.
In the presence of sunlight, CO is also transformed into CO2 during the production of photochemical smog. IOW, sunlight accelerates the oxidation of CO into CO2.
It is so flammable CO is a major component of coal gas which was a major natural gas substitute in some parts of the world. Hey folks, let’s pipe CO into people’s homes!
Note that it is only slightly lighter than air. It’s comparable to Nitrogen.
(People think that heavy gases stay near the Earth’s surface and lighter ones float to the top of the atmosphere. But they get mixed and the concentrations are uniform for any part of the atmosphere that has a significant density. CO2 outbursts from volcanic lakes and such are only dangerous for a short time until dispersion takes place.)
So unlike H and He, the amount lost to space over the eons is much more modest. Wikipedia says that an average CO molecule lasts on the orders of months before interacting chemically.
This. The vintage trope of sticking your head in an oven to commit suicide wasn’t about suffocating on natural gas, which might be somewhat challenging unless you manage to displace enough of the air in the oven. Instead, it was about poisoning yourself with the CO content of the coal gas. Exposure to CO concentration of about 1% can render you unconscious in about a minute (and dead soon after); coal gas has a CO content of about 10%, definitely enough to kill you even if it’s significantly diluted with air inside that open oven.
In lower concentrations, CO is responsible for ghost sightings and paranormal hallucinations.
Kudos to ftg! I encounter a lot of people who apparently think there is an “air” molecule (i.e., that air is an actual gas and not a mixture). Saying that a gas is “lighter than air” is a bit misleading to the average person.
The other thing to remember is that reactions always happen. This is why oily rags can spontaneously combust, why iron rusts, and so on. It’s the *rate *that is important. it’s just that in most situations the rate is slow enough to be not noticeable.
If I recall my second year chemistry Rates of Reactions lectures from over 40 years ago… If you have oil molecules and oxygen molecules bouncing around, the distribution of velocities is like a bell curve, some very fast, some very slow - the average defines temperature. The warmer the environment, the more likely that an oxygen molecule and carbon chain molecule collide with enough speed in the right way to overcome existing molecular bonds and cause an oxygen atom to bind with a carbon or hydrogen atom. What determines the number of such successful collisions is temperature (speed of molecules) and concentration or reactants (likelihood of collision). With air and a petroleum substance, another factor is how much surface area, where the two will react. In the case of oily rags you have the oil spread over a massive surface area because each fine coated thread presents a surface able to react. What makes discarded oily rags also dangerous - each reaction will give off heat (more energy) when the molecules recombine into an oxide. In a crumpled mass, this heat affects the rag rather than dissipating into the general environment, since the surrounding rag acts as an insulator. It becomes a serious feedback - the heat creates more reactions, creating more heat, until something stops it - either no more oxygen, or no more fuel, or spontaneous disassembly of the configuration…
The same would apply with CO - it would be constantly reacting with O2 at low rates of reaction. As long as the sources do not overwhelm the environment, it will slowly devolve to CO2. (Wondering if ozone in the upper atmosphere is also more reactive and more likely to contribute to this process?) I’m sure someone with a chemistry background could make a rough estimate what the general rate of reaction of CO in the atmosphere would be.
Back in the days when people denied that CFCs damaged the ozone layer one of the best arguments against it was that NASA sounding rockets showed that CFC concentrations in the atmosphere where constant up to the ozone layer and then they suddenly dropped off. I.e., the CFCs where interacting with the ozone.
(And this is also a good disproof that CFCs were too “heavy” to reach the ozone layer. If you don’t understand basic gas laws, stop doubting scientists.)
I looked to see if some similar data on CO concentrations could be found. But apparently the reaction rate, even though slow, is sufficient that very little reaches the ozone layer from ground sources.
So the short answer is - it appears that since the proportion of CO is not increasing noticeably, the reaction rate must be faster than the rate at which it is produced.
There’s a similar argument for methane in the atmosphere - it reacts with atmospheric components to break down fairly quickly. It only exists because it is constantly being replenished, one cow at a time. This is one of the suggestions for detecting life on other planets - if we detect methane and oxygen in the atmosphere, it’s probably an indicator of life, since both need to be replenished.
CO also can be metabolized by many microbes. Not that I expect that to be a major mode of atmospheric degradation.
As in this story https://www.thisamericanlife.org/319/transcript
The third bond is a dative bond. Basically a covalent bond, but instead of one electron being shared from each atom, both of the shared electrons come from the oxygen.
Thanks, all! What a great discussion! You’ve given me quite a lot to consider. I will have to re-read this post when I have more time…after the holidays.