Carbon Nanotubes PYQs MCQs

Carbon Nanotubes MCQs
NEET, IIT-JEE, IIT-JAM, GATE, CSIR-NET, DRDO

JEE Advanced 2023–2025 Expected

Q1: Carbon nanotubes were discovered by:

1. Richard Smalley
2. Sumio Iijima
3. Geim & Novoselov
4. Harold Kroto

Correct Answer: B

Sumio Iijima (NEC, Japan) discovered MWCNTs in 1991 while examining arc-discharge soot.

JEE Main 2024 Repeated

Q2: Which type of CNT always shows metallic conductivity?

1. Zigzag
2. Chiral
3. Armchair
4. All SWCNTs

Correct Answer: C

Armchair (n,n) nanotubes are always metallic due to band structure crossing at Fermi level.

CSIR-NET / GATE Classic

Q3: The chirality of a CNT is defined by the vector:

1. C = n a₁ + m a₂
2. R = n a₁ – m a₂
3. T = a₁ + a₂
4. None

Correct Answer: A

Chiral vector Cₕ = n a₁ + m a₂ completely defines rolling direction and diameter.

JEE Advanced Numerical

Q4: A (10,10) CNT is:

1. Zigzag
2. Armchair
3. Chiral
4. Semiconducting

Correct Answer: B

n = m → armchair configuration → metallic.

NEET 2025 Hot

Q5: The tensile strength of CNTs is approximately:

1. 1 GPa
2. 10 GPa
3. 100 GPa
4. 1000 GPa

Correct Answer: C (~100–200 GPa)

~100 times stronger than steel at 1/6th the density.

JEE Main 2024 Shift

Q6: The most scalable method for CNT production is:

1. Arc discharge
2. Laser ablation
3. CVD
4. HiPco

Correct Answer: C

Chemical Vapour Deposition (CVD) is low-cost and scalable for industrial production.

CSIR-NET Previous Year

Q7: SWCNTs show ballistic conduction because:

1. Mean free path > tube length
2. High defect density
3. Low mobility
4. Phonon scattering

Correct Answer: A

Electrons travel without scattering for microns → zero resistance behaviour.

JEE Advanced Assertion-Reason

Q8: Assertion: MWCNTs are always metallic.
Reason: At least one shell is metallic in MWCNT.

1. Both true, R explains A
2. Both true, R does not explain
3. A true, R false
4. A false, R true

Correct Answer: A

Conduction dominated by outermost metallic shell → overall metallic behaviour.

GATE Chemistry

Q9: The Young’s modulus of SWCNT is approximately:

1. 100 GPa
2. 1 TPa
3. 200 GPa
4. 10 TPa

Correct Answer: B (~1 TPa)

NEET Classic

Q10: CNTs are functionalised using conc. HNO₃ to introduce:

1. –OH groups
2. –COOH groups
3. –F groups
4. –NH₂ groups

Correct Answer: B

Oxidative acid treatment opens tips and attaches carboxylic groups → improves solubility.

JEE Advanced 2024 Type

Q11: Which of the following has highest thermal conductivity?

1. Diamond
2. Graphite
3. SWCNT
4. Copper

Correct Answer: C (~3500 W/m·K)

SWCNTs exceed diamond (~2000 W/m·K) along tube axis.

CSIR-NET

Q12: The rule for metallic behaviour in SWCNT is:

1. n – m divisible by 3
2. n + m divisible by 3
3. n = m
4. m = 0

Correct Answer: A

If (n – m) = 3k → metallic/semimetallic, else semiconducting.

JEE Main

Q13: CNTs are used in Li-ion batteries as:

1. Cathode
2. Anode additive
3. Electrolyte
4. Separator

Correct Answer: B

JEE Advanced Final

Q14: The diameter of a (10,10) SWCNT is approximately:

1. 0.68 nm
2. 1.36 nm
3. 2.04 nm
4. 0.34 nm

Correct Answer: B (~1.36 nm)

d = (√3 a₀ / π) √(n² + nm + m²) ≈ 1.36 nm for (10,10).

GATE 2025 Expected

Q15: The dream application of CNTs that could revolutionise space travel is:

1. Space elevator
2. Quantum computer
3. Hydrogen car
4. Transparent conductor

Correct Answer: A

Requires material with tensile strength > 50–100 GPa → only CNTs qualify.

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