Q9 of 312 Page 220

How does graphite act as a lubricant?

In graphite, each carbon atom is bonded with 3 other carbon atoms to form hexagonal rings which join together by weak Vander Waal forces to form layers. Due to the weak force, these layers can slide over each other and therefore, graphite can be used as a lubricant.

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7 Buckminsterfullerence is a spherical molecule in which 60 carbon atoms are arranged in interlocking hexagonal and pentagonal rings of carbon atoms.

(a) How many hexagons of carbon atoms are present in one molecule of buckministerfullerene?


(b) How many pentagons of carbon atoms are present in one molecule of buckministerfullerence ?

 8 Name the black substance of pencil. Will the current flow through the electrical circuit when we use the sharpened ends of the pencil to complete the circuit? 10 Name the hardest natural substance known. 11 Which of the following molecules is called buckministerfullerene?

C90 C60 C70 C120