Thread: Carbon-Oxygen Dilemma

Carbon, in it's natural state, is a solid. Oxygen is naturally a gas. In some way, carbon bonds with oxygen to form carbon dioxide. If you were to split those bonds, what would happen to carbon? Would it immediately revert to being a solid? Or would it remain in a unique gaseous state?

How would you cut the carbon oxygen bond then? Without using anything else, without any other chemicals. If you could do this, carbon would most likely form diamonds, graphite, or whatever, randomly. Carbon needs to share 4 electrons. It can't exist alone, at least i have never heard of this.

Originally Posted by jwscienceman

Carbon, in it's natural state, is a solid. Oxygen is naturally a gas. In some way, carbon bonds with oxygen to form carbon dioxide. If you were to split those bonds, what would happen to carbon? Would it immediately revert to being a solid? Or would it remain in a unique gaseous state?

Depends on how you "split" the bonds, I suppose, and on the temperature and pressure regime. If you heat CO2 to the point it dissociates thermally, you get CO at about 1300K. CO then only dissociates into atoms at above 5000K or so, at which temperature carbon may be gaseous at lowish partial pressures. The phase diagram of carbon is here: File:Carbon basic phase diagram.png - Wikimedia Commons

If you dissociate CO2 by photolysis you may (I do not know how this reaction would proceed) end up with carbon atoms below the temperature at which they condense to the solid. However I expect you get CO first and would then have to go on and photolyse this.

There are also various ways to reduce CO2 chemically or electrochemically, but the products are not generally atomic carbon.

Ah yes, plasma state. But, if you cool it down, you would have a solid anyway. Any material becomes a gas if you heat it enough. This doesn't mean carbondioxide will just remain a gas whenever oxygen is removed.

Originally Posted by Zwolver

Ah yes, plasma state. But, if you cool it down, you would have a solid anyway. Any material becomes a gas if you heat it enough. This doesn't mean carbondioxide will just remain a gas whenever oxygen is removed.

Not plasma, I don't think 5000k is hot enough for that. Molecular dissociation into atoms is what I had in mind.

Guys, I heat with wood. I know what happens to gaseos carbon at near room temperatures: It forms soot and deposits on the nearest cool surface ie: the inside of the stove pipe. Soot is graphite "fluff".

Originally Posted by Sealeaf

Guys, I heat with wood. I know what happens to gaseos carbon at near room temperatures: It forms soot and deposits on the nearest cool surface ie: the inside of the stove pipe. Soot is graphite "fluff".

It is, but I question whether it condenses from "gaseous carbon".

As the phase diagram which I linked to earlier indicates, you only get gaseous carbon above about 5000K, whereas it is relatively cool, smoky flames that are notorious for producing lots of soot. As I understand it the carbon is formed in solid particles (in the smoke), as a result of thermal cracking of components of the fuel, which then deposit on surfaces.

I really seriously doubt my wood stove reaches 5000K. Yet the carbon enters the process as a component of long chain carbohydrates, mostly celluose, and ends up as pure carbon soot. Most of it is oxidized to CO2, some exits as CO, both of which are pretty stable gases. If the carbon is not pure carbon vapor that condenses to the soot, what is the process?

Originally Posted by Sealeaf

I really seriously doubt my wood stove reaches 5000K. Yet the carbon enters the process as a component of long chain carbohydrates, mostly celluose, and ends up as pure carbon soot. Most of it is oxidized to CO2, some exits as CO, both of which are pretty stable gases. If the carbon is not pure carbon vapor that condenses to the soot, what is the process?

I think it will be thermal cracking and part-oxidation. When cellulose burns, a complex chain of reactions is initiated that breaks chains and abstracts hydrogen atoms, creating free radicals, causes bound oxygen and hydrogen to recombine as water, leaving carbon-rich species behind, and so on. Charcoal and soot are the result of this process occurring in oxygen-deficient or low temperature combustion, in which the carbohydrates lose their hydrogen and oxygen before all the carbon has been converted to CO or CO2.