8/17/2019 Graphite Question (Chemistry)

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1. Graphite is the key component of modern day pencil ‘lead’—in fact,lead is a misnomer as pencil ‘lead’ actually made up of a mixture of graphite and clay. The formulation of this mixture determines its‘lead’ grade. The higher the proportion of graphite content relativeto clay the ‘lead’ has, the softer and darker the ‘lead’ will e, and

vice versa.

 Tale 1 elow shows the various common grades of pencil leads withthe percentage values of the mass amount of graphite, clay and waxparticles.

Pencil LeadGrade

Percentage of Mass Amount / Component(%)

Graphite Clay Wax!" !# $# !

#" %& '$ !"( !#( )$ #& !!( *# 1# !

 The various graphite pencil grades are achieved y altering theproportion of graphite to clay+ the more clay the harder the pencil.

a -tate the structure of graphite. 1/

-uggest how the structure of graphite is suitale to e used as

pencil lead. #/

c 0 particular pencil is graded as ‘"(’. educe the percentage of graphite and clay in a ‘"(’ pencil. #/

d 0 pencil lead of an unknown grade, with a ‘lead’ mass of &.%*grams, is ignited and urnt completely in excess oxygen.

a. The gaseous product evolved turns moist litmus paper fromlue to red. 2dentify this gas. 1/

. 2f the gas evolved is *&& cm', deduce the grade of this pencillead. #/

e 3hen a pencil is used, sheets of graphite layers known as grapheneslide o4 the ‘lead’, and onto the 5res of the paper. The 6akes of graphene stick onto the paper 5ers. -uggest how an eraser worksto remove these graphene layers. 1/

8/17/2019 Graphite Question (Chemistry)

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f 7atural ruer erasers can e expensive tomake. "ence, synthetic erasers are made frompolyvinyl chloride 89:;, a polymer made fromethylene. raw out the structural formula of