Talk:Carbon

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Q-carbon

I propose that Q-Carbon is added to the list of carbon's solid states. reference

References

With sulfide? what state?

Quote:

with sulfur to form carbon disulfide and with steam in the coal-gas reaction:
C(s) + H2O(g) → CO(g) + H2(g).

There is no sulfur in this reaction. Does anyone know what has happened here?

I believe the problem was that these sulfur and water reactions had been cut off from their subject and verb ("Carbon reacts...") by several intervening sentences, so it didn't seem to make sense in this Old revision of Carbon. I deleted it thinking it was a non-sequitur, and now restored it with repaired grammar. --MadeOfAtoms (talk) 10:35, 15 June 2021 (UTC)

Why are we using (s) and (g) here? This is not interesting in a chemical reaction.

control the carbon content of steel:

Fe3O4 + 4 C(s) → 3 Fe(s) + 4 CO(g)

In this reaction, iron is molten, not solid (s). Fe3O4 does not have (s). I suggest we just drop these phase (state) designations in these equations. This is the first in about 30 pages where they appear. Consensus?

Regarding removed text

I just removed the sentence "In July 2020, astronomers reported evidence that carbon was formed mainly in white dwarf stars, particularly those bigger than two solar masses." from the section on Occurrence. This section cited an Inverse article and the journal article that said Inverse article itself cites.

However, the sentence is not supported by the journal article (it essentially parrots the Inverse article, which is a gross misinterpretation).

Most of the carbon in the universe is in white dwarf stars. This is basic knowledge of astrophysics and uncontested. However, this carbon is not relevant to things such as planetary formation and the composition of new stars; it is confined in the white dwarf essentially permanently. Thus, astrophysicists often talk of the sources of carbon in the interstellar medium - i.e., that not locked in remnants. As carbon is only formed in stars, this translates to the various ways that stars can shed material enriched in carbon - the main contributors to this are the stellar wind of dying AGB stars (which will eventually leave behind white dwarfs, but are not yet such), and core-collapse supernovae. White dwarfs can shed material into space via type Ia supernovae; however, this is not thought to be a major contribution to carbon abundance in the ISM.

(In terms of nuclear origin, white dwarfs produce no carbon except a miniscule amount during helium novae. Carbon is created via the triple-alpha process in the cores of AGB stars, red supergiants, and the various higher-mass evolved stars such as LBVs and Wolf-Rayet stars.)

What the paper claims is that AGB stars in a certain range of initial mass (1.6-1.9) have weaker stellar winds than previously thought, and therefore contribute very little carbon to the ISM (as more of it is deposited in the white dwarf remnant). It does not claim that the source of carbon (either in terms of nuclear origin or dispersal into ISM) is white dwarfs.

(As an aside, the mention of "white dwarf stars... bigger than two solar masses" is nonsense. White dwarfs cannot have masses that high, due to the Chandrasekhar limit. The mass of a white dwarf is much lower than the initial mass of the star that produced it; the journal article asserts that stars of initial mass 1.5-2.8 solar masses all leave white dwarfs of masses 0.6-0.75 solar masses, though the dependence is - this is the point of the article - not monotonic.) Magic9mushroom (talk) 12:27, 1 May 2021 (UTC)

Melting point of diamond

User:Eric Kvaalen, as a complete non-expert I'm a bit confused by the note you added to the phase diagram in the intro, and looking to improve it. Firstly, the link referenced seems to be about the melting point of diamond ("shock-compressed" diamond, whatever that really means), which does not include the melting point of Graphite listed in the table, so this needs to be clarified. Second, is the note saying the upper line between Diamond and Liquid is wrong and should be edited? Is there a pressure-temp phase diagram from the paper that we could include here instead?

Finally, would it be better to include this note in the text, rather than in the figure? Thanks! Cstanford.math (talk) 12:49, 4 October 2021 (UTC)

@Cstanford.math: Hello. Yes, the title of the reference is "Melting temperature of diamond at ultrahigh pressure", because it's looking at the melting point at high pressures where the solid would be diamond. "Shock-compressed" means that they shoot a laser at a small disk of diamond, or actually at a thin coat of aluminum if I remember right on the small disk of diamond, and this causes very rapid ablation of the aluminum, which acts like a rocket engine you could say, causing a shock wave to travel through the carbon. This shock wave causes the carbon to go very briefly to very high temperatures and pressures, and they can actually figure out what the path through T-P space is. I don't know what table you are referring to. It's true that the melting point of diamond (which depends on pressure) is not the same as the melting point of graphite (which also depends on pressure), except at the "triple point" where graphite, diamond, and liquid carbon are all in equilibrium. Yes, the graph is wrong at the upper right. Instead of continuing to curve to the right, it should curve upwards toward higher pressure without ever surpassing 9000 K in temperature. Yes, there is a diagram in the paper, but of course somebody would have to make a copy as an SVG file or whatever. Fortunately the article is open-access. Yes, we could put something in the text, but I thought it was more important to modify the caption because people need to know that the curve is wrong. Anyway, people don't always read the text very carefully. Eric Kvaalen (talk) 09:17, 5 October 2021 (UTC)

That all makes sense, thanks! I clarified the figure caption based on what you wrote here. Mainly, I wasn't sure which part of the phase diagram the caption was correcting, but I think it's clear now. Feel free to improve further. Cstanford.math (talk) 16:39, 5 October 2021 (UTC)

Carbon

How can diamond be created by putting pressure on carbon how is it possible? 147.92.91.58 (talk) 04:06, 23 November 2021 (UTC)

carbon

carbon 27.61.213.169 (talk) 10:31, 31 December 2021 (UTC)