Question

A Graphite has a layer like structure.
B. The distance between two layers in graphite is 20 pm
C. Each layer is composed of planar hexagonal rings
Which of the above statement (s) is /are true?

• A. A & C
• B. A & B
• C. only A
• D. A, B & C

Answer 1

The correct option is A A & C

(A) Graphite has a layered structure held by van der Waals forces
(B) The distance between two layers is 340 pm.
(C) Each layer is composed of planar hexagonal rings of $s{p}^2$ hybridized carbon atoms. Each C atom in hexagonal ring make three sigma bonds with three neighboring C atoms and the fourth electron forms a $\pi$ bond.

THEORY
Graphite:

• Graphite has a layered structure held by van der Waals forces and the distance between the two layers is 340 pm.
• Each layer is composed of planar hexagonal rings of $s{p}^2$ hybridized carbon atoms.
• Each C atom in a hexagonal ring makes three sigma bonds with three neighboring C atoms and the fourth electron forms a 𝜋 bond.
• Electrons are mobile and delocalized over the whole sheet therefore graphite conducts electricity along with the sheet.
• Graphite cleaves easily between the layers; hence it is very soft and slippery.
• Graphite is used as a dry lubricant in machines running at high temperatures, where oil can not be used as a lubricant.
• Graphite is thermodynamically most stable allotrope of carbon, hence $\Delta H{f}^o$ of graphite is taken as zero.
• $\Delta H_f^o\text{of diamond}=1.90kJmo{l}^{-1}$
• $\Delta H_f^o\text{of Fullerene}\left(C_{60}\right)=38.1kJmo{l}^{-1}$
• Other forms of elemental carbon like carbon black, coke and charcoal are all impure forms of graphite or fullerenes.
• Carbon black is obtained by burning hydrocarbons in a limited supply of air. Charcoal and coke are obtained by heating wood or coal respectively at high temperatures in the absence of air.
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