Paper II · Part B — Chemistry

Carbon and its Forms (Allotropes)

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Core5 mapped NDA questions

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Build exam-ready understanding by connecting the core idea, formulas or facts, worked example and previous NDA questions. Focus on why each rule works, then test it under timed conditions.

Concept

Carbon is a versatile element forming millions of compounds. Its allotropes (different structural forms of the same element) include diamond, graphite and fullerenes, each with very different properties.

Allotropy is the same element existing in different physical forms.

Key Points & Formulas

Diamond: hardest natural substance; each carbon bonded to four others.
Graphite: soft, slippery, conducts electricity; used in pencils and as a lubricant.
Both diamond and graphite are pure carbon — allotropes.
Carbon forms covalent compounds (organic chemistry).

Worked Example

Q. Graphite conducts electricity but diamond does not. Why?

In graphite each carbon bonds to only three others, leaving free electrons.

These free electrons carry current.

In diamond all four electrons are bonded, leaving none free — so it does not conduct.

Common traps

Reading the prompt too quickly and missing a qualifier.
Memorising the result without checking when it applies.
Skipping units, signs, chronology or the final reasonableness check.

NDA shortcuts

State the governing rule before substituting values.
Eliminate impossible options before doing full calculation.

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Core definition
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Past-paper bank

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Filter by year

5 NDA questions

Choose an answer before the solution appears. Option order is mixed automatically.

Question 1

NDA I 2026

Which one of the following forms of carbon is thermodynamically most stable?

Question 2

NDA I 2024

Match List-I with List-II and select the correct answer using the code given below the Lists:

List-I (Allotrope of Carbon)
A. Graphite
B. Diamond
C. Fullerene
D. Graphene

List-II (Property)
1. Thinnest and strongest material
2. Hardest natural substance
3. Very light and strong material
4. Soft and slippery material

Code:

Question 3

NDA II 2023

Which among the following statements with respect to carbon is/are correct?
1. Carbon forms the basis for all living organisms and many things we use
2. Carbon shows tetra-valency and the property of catenation
3. Carbon forms covalent bonds with itself and other elements
4. Carbon forms compounds containing triple and tetra bonds between carbon atoms
Select the correct answer using the code given below:

Question 4

NDA I 2023

Which among the following statements is NOT correct with respect to allotropes of Carbon?

Question 5

NDA II 2023

Buckminster fullerene, which looks like a football, is an allotropic form of

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