CDS Questions on Carbon and its Allotropes

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CDS 2013-I

1. Which allotrope of carbon is in rigid three-dimensional structure?

  1. Graphite
  2. Fullerene
  3. Diamond
  4. Carbon black

CDS 2014-II

2. The form of carbon known as graphite

  1. is harder than diamond
  2. contains a higher percentage of carbon than diamond
  3. is a better electrical conductor than diamond
  4. has equal carbon-to-carbon distances in all directions

CDS 2015-I

3. Which one among the following is used in making lead pencils?

  1. Charcoal
  2. Graphite
  3. Coke
  4. Carbon black

CDS 2015-II

4. Which one of the following is not true for diamond?

  1. Each carbon atom is linked to four other carbon atoms
  2. Three-dimensional network structure of carbon atoms is formed
  3. It is used as an abrasive for sharpening hard tools
  4. It can be used as a lubricant

CDS 2016-II

5. Which one of the following is NOT an allotrope of carbon?

  1. Coal
  2. Diamond
  3. Graphite
  4. Graphene

CDS 2018-II

6. Which one of the following is NOT true for the form of carbon known as diamond?

  1. It is harder than graphite
  2. It contains the same percentage of carbon as graphite
  3. It is better electric conductor than graphite
  4. It has different carbon to carbon distance in all directions

CDS 2019-II

7. In graphite, each carbon atom is bonded to three other carbon atoms

  1. forming a three-dimenstional structure
  2. in the same plane giving a hexagonal array
  3. in the same plane giving a square array
  4. in the same plane giving a pentagonal array

CDS 2021-II

8. Which of the following carbon allotropes is/are good conductor(s) of electricity?

  1. Diamond
  2. Graphite
  3. Fullerene

Select the correct answer using the code given below:

  1. 1 only
  2. 1 and 2 only
  3. 2 only
  4. 1 and 3 only

CDS 2023-II

9. Which one of the following statements is correct about diamond and graphite?

  1. Diamond and graphite have similar physical and chemical properties.
  2. Diamond is hard but graphite is smooth and slippery.
  3. Diamond and graphite are both non-conductors of electricity.
  4. Both diamond and graphite have similar structures.

Carbon and its Allotropes

Carbon is a chemical element with atomic number 6 and symbol C. Carbon has 4 valence electrons in its outermost shell and its valency is 4. The atoms of carbon may bond to each other in different ways forming various allotropes. The most common allotropes of carbon are diamond, graphite and fullerene.

Difference between Diamond and Graphite

DiamondGraphite
In diamond each carbon atom is bonded to four other carbon atoms forming a rigid three-dimensional structure.In graphite, each carbon atom is bonded to three other carbon atoms in the same plane giving a hexagonal array.
Diamond is the hardest substance known.Graphite is smooth and slippery.
Diamond is used in cutting of glass and other diamonds.Graphite is used in making of pencils, lubricants and brushes of electric motors.
Diamond is a poor conductor of electricity.Graphite is a good conductor of electricity.
Diamond is transparent and has a refractive index of 2.42 to 2.45.Graphite is opaque.

Important points about carbon and its forms

  • Diamonds can be artificially produced by subjecting pure carbon to very high pressure and temperature and such artificial diamonds are barely distinguishable from natural diamonds.
  • Coal is NOT a pure form of carbon. Different types of coal contain various amounts of carbon along with other impurities.
  • Fullerene which has a geodesic dome like structure is another allotrope of carbon.
  • Graphene is a single layer of carbon atoms arranged in a two-dimensional honeycomb lattice structure.
  • Coal and charcoal are not considered allotropes of carbon as they contain certain impurities.

CDS Solved Papers

CDS 2021 - I Solved Paper CDS 2021 - II Solved Paper CDS 2022 - I Solved Paper CDS 2022 - II Solved Paper CDS 2023 - I Solved Paper CDS 2023 - II Solved Paper