Graphene PYQs MCQs

Graphene MCQs
NEET, IIT-JEE, IIT-JAM, GATE, CSIR-NET

JEE Advanced 2018, 2022 Pattern

Question 1: Graphene is best described as

1. a zero band-gap semiconductor
2. a direct band-gap semiconductor
3. a wide band-gap insulator
4. a pure metal

Correct Answer: A

Explanation:
In graphene, the valence band and conduction band touch at six Dirac points → zero band gap. It behaves as a semi-metal or zero-band-gap semiconductor.
B is wrong → band gap is zero, not finite direct.
C is wrong → it is highly conducting, not insulator.
D is wrong → metals have overlapping bands, but graphene has linear dispersion (Dirac cones), not parabolic.

GATE & CSIR-NET Repeated

Question 2: The most industrially viable method for large-area, high-quality graphene is

1. Mechanical exfoliation (scotch tape)
2. Chemical Vapour Deposition (CVD)
3. Reduction of graphene oxide
4. Liquid phase exfoliation

Correct Answer: B

Explanation:
CVD on copper foil at ~1000°C using CH₄/H₂ gives continuous, large-area, transferable graphene of excellent quality — used in touchscreens and flexible electronics.
A → gives highest quality but only micron size.
C → cheap but many defects, low mobility.
D → gives few-layer graphene with solvent contamination.

JEE Advanced

Question 3: Each carbon atom in graphene is

1. sp hybridized
2. sp² hybridized
3. sp³ hybridized
4. sp³d hybridized

Correct Answer: B

Three σ bonds in plane + one π bond perpendicular → classic sp² hybridization (same as benzene).
A → sp → linear (acetylene).
C → sp³ → tetrahedral (diamond).
D → never for carbon.

CSIR-NET / GATE

Question 4: Theoretical specific surface area of single-layer graphene is

1. 500 m²/g
2. 1315 m²/g
3. 2630 m²/g
4. 5000 m²/g

Correct Answer: C

Both sides of the sheet are accessible → 2630 m²/g (standard value quoted in all textbooks and papers).
B → considers only one side.
A & D → far from actual value.

JEE Advanced

Question 5: A single layer of graphene is

1. completely opaque
2. absorbs ~2.3% of visible light
3. absorbs ~23% of visible light
4. absorbs ~50% of visible light

Correct Answer: B

Universal optical conductivity → absorbance = πα ≈ 2.3% per layer (Nobel prize experiment).
Hence even stacked 10 layers appear faintly visible on SiO₂ substrate.

GATE

Question 6: Young’s modulus of graphene is approximately

1. 200 GPa (steel)
2. 1 TPa
3. 10 TPa
4. 0.1 TPa

Correct Answer: B

Measured by nanoindentation using AFM → ~1 TPa (1000 GPa) → ~200 times stronger than steel by weight.

CSIR-NET

Question 7: Graphene was first isolated in 2004 by

1. Sumio Iijima
2. Richard Smalley
3. Andre Geim and Konstantin Novoselov
4. Harry Kroto

Correct Answer: C

Using scotch-tape method → Nobel Prize in Physics 2010.

JEE Advanced

Question 8: Charge carriers in graphene behave as

1. ordinary electrons with effective mass
2. massless Dirac fermions
3. photons
4. Cooper pairs

Correct Answer: B

Linear E–k dispersion → relativistic Dirac equation → carriers behave as massless particles moving at ~c/300.

GATE / CSIR-NET

Question 9: Graphene oxide (GO) is

1. highly conducting like graphene
2. hydrophobic
3. insulating and hydrophilic
4. superconducting

Correct Answer: C

Oxygen functional groups (–OH, –COOH, epoxide) disrupt sp² network → opens band gap → becomes insulator and water-dispersible.

JEE Main / NEET

Question 10: Thickness of one graphene layer is

1. 0.34 nm
2. 3.4 nm
3. 34 nm
4. 0.034 nm

Correct Answer: A

Interlayer distance in graphite = 0.335–0.34 nm → taken as thickness of single layer.

CSIR-NET

Question 11: Maximum reported room-temperature electron mobility in suspended graphene is

1. ~2000 cm²/V·s (silicon)
2. ~15,000 cm²/V·s
3. ~2,50,000 cm²/V·s
4. ~10⁶ cm²/V·s

Correct Answer: C

Highest ever recorded for any material at room temperature.

JEE Advanced

Question 12: C–C bond length in graphene is

1. 0.154 nm (C–C single)
2. 0.142 nm
3. 0.134 nm (C=C double)
4. 0.120 nm (C≡C triple)

Correct Answer: B

Intermediate between single and double → delocalized π bonding.

JEE Advanced

Question 28: Which property is NOT possessed by pristine graphene?

1. High thermal conductivity
2. High mechanical strength
3. Tunable direct band gap
4. High electron mobility

Correct Answer: C

Tricky eliminator: Tunable direct band gap is property of phosphorene and transition metal dichalcogenides (TMDs), not graphene. Graphene has zero band gap.

GATE / CSIR-NET

Question 29: Hummers method is used for preparation of

1. Pristine graphene
2. Graphene oxide
3. Carbon nanotubes
4. Fullerene

Correct Answer: B

Strong oxidants (KMnO₄ + H₂SO₄) → graphite → graphene oxide.

JEE Advanced / CSIR-NET

Question 30: The thermal conductivity of graphene (~5000 W/m·K) is higher than that of

1. Diamond (~2000 W/m·K)
2. Copper (~400 W/m·K)
3. Silver (~429 W/m·K)
4. All of the above

Correct Answer: D

Graphene has the highest thermal conductivity of any known material.

GATE & CSIR-NET Repeated

Graphene is used as transparent conductive electrode in touchscreens and OLEDs because it has

1. 97.7% optical transparency + high conductivity
2. zero band gap only
3. very high band gap
4. low mechanical strength

Correct: A

Graphene combines ~97.7% transparency in visible region with sheet resistance <20 Ω/sq → superior replacement for brittle & costly ITO (Indium Tin Oxide).

JEE Advanced 2023 Pattern

In next-generation lithium-ion batteries, graphene is added to

1. cathode only
2. anode only (as conductive additive or Si-graphene composite)
3. electrolyte
4. separator

Correct: B

Graphene improves conductivity, accommodates volume expansion of silicon anodes, and enables ultra-fast charging (e.g., Tesla & Samsung prototypes).

CSIR-NET / GATE

Graphene-based ultracapacitors (supercapacitors) offer

1. very high energy density but low power density
2. very high power density and long cycle life
3. low power density
4. same performance as Li-ion batteries

Correct: B

EDLC mechanism + 2630 m²/g surface area → power density >10 kW/kg and >1 million cycles.

JEE Advanced

Graphene is used in anti-corrosion coatings because

1. it is impermeable to gases and ions
2. it reacts with oxygen
3. it has low conductivity
4. it absorbs water

Correct: A

Single-layer graphene is the thinnest known barrier — even He atoms cannot pass through defect-free graphene.

GATE 2024

Graphene oxide (GO) membranes are highly efficient in

1. for sea-water desalination
2. for oil separation
3. for gas separation (CO₂/N₂)
4. all of the above

Correct: D

2D nanochannels in GO laminates allow water molecules but block hydrated ions, salts, and larger molecules.

CSIR-NET

In flexible and wearable electronics, graphene is preferred over ITO because

1. ITO is flexible
2. Graphene is flexible, stretchable and does not crack on bending
3. ITO is cheaper
4. ITO has higher conductivity

Correct: B

ITO is brittle and cracks after few bending cycles; graphene can withstand >30% strain.

JEE Advanced

Graphene-enhanced polymer composites are used in

1. aircraft (Boeing 787, Airbus A350)
2. sports equipment (tennis rackets, bicycles)
3. automotive parts
4. all of the above

Correct: D

Even 0.1 wt% graphene increases strength by 50–100% and reduces weight.

GATE

Graphene is used in thermal interface materials (TIMs) because its thermal conductivity is

1. ~5000 W/m·K (higher than diamond)
2. ~400 W/m·K (same as copper)
3. ~2000 W/m·K
4. ~100 W/m·K

Correct: A

Used in CPU/GPU cooling, 5G devices, and electric vehicles.

CSIR-NET 2023

Graphene quantum dots (GQDs) are used in

1. bio-imaging and drug delivery
2. structural composites
3. battery cathodes
4. none

Correct: A

GQDs show size-dependent fluorescence and low toxicity → ideal for biomedical applications.

JEE Advanced / GATE

Which application does NOT use graphene?

1. Quantum computing qubits
2. DNA sequencing (nanopore method)
3. High-frequency transistors (>500 GHz)
4. Primary structural material of rockets (currently)

Correct: D

Rockets still use carbon fiber composites; graphene is only in coatings and electronics so far.

Must Read Chemistry of Graphene