Chemistry 9th Chap 2 : Topic 4 - Maryam Publications

Chemistry Chapter 2 : Topic 4

Allotropes of Carbon

1 / 20

Carbon exists in different structural forms known as allotropes. Which statement best explains the concept of allotropy in solids?

A) Elements that exist in only one crystalline form under all conditions

B) Mixtures of carbon with impurities that change its color and hardness

C) Different compounds formed by carbon with other elements like oxygen and hydrogen

D) Different structural forms of the same element having different physical properties but same chemical nature

2 / 20

Diamond is an allotrope of carbon with unique properties. Which statement correctly explains why diamond is extremely hard?

A) It has weak intermolecular forces between carbon molecules

B) Carbon atoms are arranged in layers that can easily slide over each other

C) It contains free electrons that weaken the atomic structure

D) Each carbon atom forms four strong covalent bonds in a rigid three-dimensional tetrahedral structure

3 / 20

Graphite is also an allotrope of carbon. Which feature explains why graphite is used in pencils?

A) It is completely insoluble in water due to ionic bonding

B) It is the hardest known natural substance

C) It contains no covalent bonds between carbon atoms

D) It has a layered structure with weak forces between layers allowing easy sliding

4 / 20

Which statement best distinguishes diamond from graphite?

A) Diamond has a 3D network structure while graphite has a layered structure

B) Diamond conducts electricity while graphite does not

C) Both have identical structures but different atomic numbers

D) Graphite is harder than diamond due to free electrons

5 / 20

Graphite is a good conductor of electricity because:

A) It contains freely moving electrons between layers

B) All carbon atoms are completely ionized

C) It contains water molecules between carbon layers

D) It has metallic bonds throughout its structure

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Fullerenes are an allotrope of carbon discovered later than diamond and graphite. Which statement correctly describes fullerenes?

A) Linear chains of carbon atoms

B) Infinite flat layers of carbon atoms

C) Spherical or cage-like structures made of carbon atoms

D) Random mixtures of carbon and hydrogen

7 / 20

Which property is common to all allotropes of carbon (diamond, graphite, fullerenes)?

A) Same arrangement of atoms in all structures

B) Same chemical nature but different structural arrangements

C) Same melting and boiling points

D) Same physical properties like hardness and conductivity

8 / 20

Why does diamond not conduct electricity, although it is made of carbon?

A) All electrons are involved in strong covalent bonding with no free electrons

B) It has free electrons that are trapped

C) It dissolves electrons in its structure

D) It contains ionic bonds instead of covalent bonds

9 / 20

Which statement correctly compares graphite and diamond?

A) Graphite is soft due to layers while diamond is hard due to 3D bonding

B) Both have layered structures and are soft

C) Diamond is layered while graphite is a giant network solid

D) Both are conductors of electricity due to free ions

10 / 20

The lubricating property of graphite is due to:

A) Presence of metallic bonding

B) Strong covalent bonds between layers

C) Weak forces between carbon layers allowing them to slide

D) Its ability to dissolve in oils

11 / 20

Fullerenes differ from diamond and graphite because:

A) They have no covalent bonds

B) They form hollow cage-like molecular structures

C) They are ionic solids

D) They are made only of oxygen atoms

12 / 20

Which property makes diamond suitable for cutting and drilling tools?

A) High electrical conductivity

B) Extreme hardness due to strong 3D covalent bonding

C) Soft layered structure

D) Low melting point

13 / 20

Why is graphite used in electrodes?

A) It is a poor conductor of heat

B) It is extremely hard and does not react

C) It has ionic bonding structure

D) It is a good conductor of electricity due to delocalized electrons

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Which statement about carbon allotropes is incorrect?

A) Graphite is soft and slippery

B) Fullerenes are spherical carbon molecules

C) Diamond conducts electricity due to free electrons

D) Diamond is transparent and very hard

15 / 20

The difference in physical properties of diamond and graphite is mainly due to:

A) Different chemical reactions with oxygen

B) Different arrangements of carbon atoms and bonding structure

C) Different atomic numbers of carbon atoms

D) Presence of different elements in each allotrope

16 / 20

Which allotrope of carbon is considered the most stable under normal conditions?

A) Graphite

B) Carbon monoxide

C) Diamond

D) Fullerene

17 / 20

In fullerenes (C₆₀), carbon atoms are arranged in:

A) Tetrahedral 3D network

B) Hexagonal flat sheets only

C) Linear chains of atoms

D) Combination of pentagons and hexagons forming a spherical shape

18 / 20

Which statement best explains why graphite can be used as a dry lubricant?

A) Its layers can easily slide over each other due to weak intermolecular forces

B) It reacts with metals to form slippery compounds

C) It has strong ionic bonds

D) It is liquid at room temperature

19 / 20

Why are fullerenes important in modern nanotechnology?

A) They are completely inert gases

B) They conduct electricity like metals in all conditions

C) They are the hardest known materials

D) They have hollow structures suitable for drug delivery and nanodevices

20 / 20

Which statement correctly summarizes the nature of carbon allotropes?

A) They are mixtures of carbon with other non-metals

B) They are different elements formed by carbon reactions

C) They are identical substances with identical structures

D) They are different structural forms of carbon with distinct physical properties

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