## Carbon as graphite [ENDORSED]

Christina Cen 2J
Posts: 53
Joined: Sat Jul 22, 2017 3:01 am

### Carbon as graphite

Can someone explain to me again why carbon is more stable as graphite and why in 67 b, it isn't a gas like hydrogen and oxygen?

Ashin_Jose_1H
Posts: 51
Joined: Fri Sep 29, 2017 7:04 am

### Re: Carbon as graphite

In 67b, C(gr) means that we are looking at Carbon in graphite form. I'm not too sure on why Carbon is more stable as graphite.

Xihui Yin 1I
Posts: 40
Joined: Fri Sep 29, 2017 7:06 am

### Re: Carbon as graphite

In the graphite form, carbon is sp2 bonded to 3 other carbon atoms to form a hexagonal ring. However, each C still has a spare 2p orbital containing an electron. The 2p orbitals overlap to form a delocalised pi bonding system and as such, rings of carbons exist as individual sheets. Dispersion forces exist between these sheets and results in stability.

Pooja Nair 1C
Posts: 55
Joined: Thu Jul 13, 2017 3:00 am

### Re: Carbon as graphite

Because you are finding the standard enthalpy, you have to use the elements in their most stable state. For hydrogen and oxygen, the most stable form is in H2 and O2 gas, but for carbon, the most stable state is as graphite.

Jana Sun 1I
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Joined: Sat Jul 22, 2017 3:00 am

### Re: Carbon as graphite

This might be going on a limb, but I thought carbon's most stable form was as diamond. Can someone explain why/how graphite is most stable than diamond?

Abel Thomas 2C
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### Re: Carbon as graphite

In graphite, carbon is sp2 hybridized and possesses free electrons which are delocalized. In diamond, carbon is sp3 hybridized and there are no free electrons. Delocalization is what makes graphite more stable than diamond, since there are more van der waals interactions.

Chem_Mod
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### Re: Carbon as graphite  [ENDORSED]

To expand on what other students have been saying, graphite exists as layers of graphene sheets. These sheets, like previously described, consist of sp$^{2}$
hybridized carbons, essentially like a bunch of benzenes all chained together in a continuous sheet. This delocalizes electrons, making it a stable structure. Additionally, the sheets undergo $\pi -\pi$ stacking, which consists of interactions between the positive center of the rings and the negative exterior, which further stabilizes the structure. Diamond is actually less stable and degrades over time back to graphite, so saying that diamonds are forever is technically untrue.

Hellen Truong 2J
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### Re: Carbon as graphite

When using C(gr) to solve for reaction enthalpies using the bond enthalpy method, why would you add the atomization or sublimation of carbon (+717kj/mol)?