Why does graphite conduct electricity while diamond does not?
- A.Graphite contains metal impurities
- B.Each carbon atom in graphite has one free electron
- C.Graphite is made of a different element
- D.Diamond has a lower melting point
Correct answer
Explanation
The correct answer is B. In graphite every carbon atom is bonded to only three others within a layer, so the fourth valence electron of each atom is free to move along the layer, and moving electrons constitute an electric current. Option A is wrong because pure graphite conducts by itself; impurities are not the reason, and the same conduction is seen in synthetic graphite of high purity. Option C is wrong because diamond and graphite are both made of carbon alone, which is the whole point of calling them allotropes; only the arrangement of atoms differs. Option D is wrong because diamond actually has an extremely high melting point owing to its rigid three-dimensional network, and melting point in any case does not decide conduction. In diamond each atom is bonded to four others, so no electron is left free.
Read the full article: Carbon and Its Compounds: Bonding, Allotropes and PYQs
Practice Questions
View allCooking gas (LPG) mainly consists of
- A.Ethene
- B.Ethyne
- C.Propene
- D.Propane and Butane
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Liquefied petroleum gas is a mixture of these two saturated hydrocarbons, which are gases at ordinary pressure but turn liquid under moderate pressure, so a large quantity of fuel fits into a small cylinder; a strong-smelling compound is added so that a leak is noticed.
Read the full explanation →How many isomers does C6H14 have?
- A.3
- B.6
- C.4
- D.5
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Hexane, C6H14, can be drawn as a straight chain of six carbons, as two chains of five carbons with a methyl branch in different positions, and as two chains of four carbons carrying branches, which gives five different structures with the same molecular formula.
Read the full explanation →Compounds with exactly two double carbon to carbon bonds are known as ______.
- A.Terpenes
- B.Dienes
- C.Trialkyne
- D.Dialkyne
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The prefix di stands for two and the ending ene for a carbon to carbon double bond, so a diene is a hydrocarbon carrying exactly two such bonds; buta-1,3-diene, the raw material of synthetic rubber, is the standard example.
Read the full explanation →The first member of the alkyne group of hydrocarbons is
- A.propyne
- B.ethyne
- C.methyne
- D.butyne
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An alkyne contains a carbon to carbon triple bond, which needs at least two carbon atoms, so the series begins with ethyne, C2H2, also called acetylene and used with oxygen in welding.
Read the full explanation →A gas stove flame burns blue because of
- A.Complete combustion of fuel
- B.Presence of hydrogen in the air
- C.Hazardous combustion
- D.Insufficient oxygen
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When enough air reaches the burner, every carbon atom of the fuel is oxidised fully to carbon dioxide and the flame is blue and hot, giving the maximum heat for the gas consumed.
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