Problem 97 - Chemistry: The Central Science

Question

Which statement correctly describes a difference between graphene and graphite? (a) Graphene is a molecule but graphite is not. (b) Graphene is a single sheet of carbon atoms and graphite contains many, and larger, sheets of carbon atoms. (c) Graphene is an insulator but graphite is a metal. (d) Graphite is pure carbon but graphene is not. (e) The carbons are \(s p^{2}\) hybridized in graphene but \(s p^{3}\) hybridized in graphite.

Step-by-Step Solution

Answer

(b) Graphene is a single sheet of carbon atoms, and graphite contains many and larger sheets of carbon atoms.

Step 1: Review of Graphene

Graphene is a single layer of carbon atoms arranged in a two-dimensional honeycomb lattice. Each carbon atom is \(sp^{2}\) hybridized and forms three sigma bonds with its neighboring carbon atoms, leaving one electron in the \(2p_z\) orbital free to move, which provides graphene with its excellent electrical conductivity.

Step 2: Review of Graphite

Graphite is made up of multiple layers of graphene stacked on top of one another. The layers are held together by weak van der Waals forces, which allow them to slide over each other, giving graphite its lubricating properties. Each carbon atom in graphite is also \(sp^{2}\) hybridized, and due to the large number of layers in most graphite samples, it has a larger overall structure than a single layer of graphene. Now let's evaluate each option.

Step 3: Option (a)

Graphene is a molecule but graphite is not. This statement is incorrect because graphene, being an infinitely extending 2D sheet, is not considered a molecule (which typically have a finite number of atoms).

Step 4: Option (b)

Graphene is a single sheet of carbon atoms and graphite contains many, and larger, sheets of carbon atoms. This statement is correct since graphene is a single layer 2D sheet of carbon atoms, while graphite is formed by stacking many graphene sheets.

Step 5: Option (c)

Graphene is an insulator but graphite is a metal. This statement is incorrect. Both graphene and graphite are good electrical conductors due to the delocalized electrons in their \(sp^{2}\) hybridized carbon lattice, so neither of them is an insulator.

Step 6: Option (d)

Graphite is pure carbon but graphene is not. This statement is incorrect because both graphene and graphite are allotropes of carbon, meaning both are composed purely of carbon atoms.

Step 7: Option (e)

The carbons are \(sp^{2}\) hybridized in graphene but \(sp^{3}\) hybridized in graphite. This statement is incorrect, as both graphene and graphite have \(sp^{2}\) hybridized carbon atoms. Therefore, the correct answer is:

Step 8: Answer

(b) Graphene is a single sheet of carbon atoms, and graphite contains many and larger sheets of carbon atoms.