Black Phosphorous PYQs MCQs

Black Phosphorous MCQs
NEET, IIT-JEE, CSIR-NET, GATE, IIT-JAM

JEE Advanced 2020, 2022

Question: The thermodynamically most stable allotrope of phosphorus is

1. White phosphorus
2. Red phosphorus
3. Black phosphorus
4. Violet phosphorus

Correct Answer: C

Explanation: Stability order: Black > Red > White. Black phosphorus has the lowest energy state under normal conditions.

GATE & CSIR-NET Repeated

Question: Black phosphorus is prepared by

1. heating white P at 573 K in inert atmosphere
2. heating white P under high pressure (∼12,000 atm) at 473 K
3. heating red P in sealed tube
4. direct reaction of P₄ with graphite

Correct Answer: B

Explanation: Bridgman method: White P is subjected to very high pressure (∼12,000 atm) at 200°C → orthorhombic black P.

JEE Advanced

Question: The structure of black phosphorus is

1. molecular (P₄)
2. amorphous polymeric
3. layered (2D puckered sheets)
4. chain polymer like red P

Correct Answer: C

Explanation: Orthorhombic black P has corrugated (puckered) layered structure similar to graphite → van der Waals forces between layers.

CSIR-NET / GATE

Question: Black phosphorus is

1. best conductor of electricity among phosphorus allotropes
2. insulator
3. semiconductor with zero band gap
4. superconductor

Correct Answer: A

Explanation: It is a semiconductor (band gap ∼0.3 eV) and best conductor among allotropes due to delocalized electrons in puckered layers.

JEE Advanced

Question: Each phosphorus atom in black phosphorus is covalently bonded to

1. 2 other P atoms
2. 3 other P atoms
3. 4 other P atoms
4. 5 other P atoms

Correct Answer: B

Explanation: Like red P, each P atom forms 3 covalent bonds in the puckered layer.

GATE

Question: Black phosphorus has metallic lustre and is

1. opaque and brittle
2. transparent
3. soft and waxy
4. gaseous

Correct Answer: A

JEE Advanced 2023 Pattern

Question: Black phosphorus is chemically

1. most reactive
2. least reactive
3. moderately reactive
4. as reactive as white P

Correct Answer: B

Explanation: Due to strong covalent bonding and absence of strain, it is the least reactive allotrope.

CSIR-NET

Question: Exfoliated single layer of black phosphorus is known as

1. Graphene
2. Phosphorene
3. Silicene
4. Germanene

Correct Answer: B

Explanation: Phosphorene is a 2D material with excellent semiconductor properties.

JEE Main / NEET

Question: Black phosphorus does NOT show

1. chemiluminescence
2. layered structure
3. semiconducting property
4. metallic lustre

Correct Answer: A

GATE

Question: Density of black phosphorus is

1. 1.82 g/cm³
2. 2.1 g/cm³
3. 2.69 g/cm³
4. 3.5 g/cm³

Correct Answer: C

Explanation: Highest density among allotropes → 2.69 g/cm³

JEE Advanced

Question: Black phosphorus is insoluble in

1. water
2. CS₂
3. both A and B
4. benzene

Correct Answer: C

CSIR-NET

Question: Black phosphorus ignites in air at

1. 30°C
2. 260°C
3. above 400°C
4. does not ignite

Correct Answer: C

JEE Advanced

Question: The interlayer forces in black phosphorus are

1. covalent
2. ionic
3. van der Waals
4. metallic

Correct Answer: C

GATE

Question: Black phosphorus is isomorphous with

1. graphite
2. diamond
3. white phosphorus
4. red phosphorus

Correct Answer: A

Explanation: Both have puckered layered structure.

NEET Level

Question: Which allotrope of phosphorus is non-poisonous and most stable?

1. White
2. Red
3. Black
4. All are poisonous

Correct Answer: C

JEE Advanced

Question: Phosphorene shows

1. direct band gap
2. indirect band gap
3. zero band gap
4. metallic behaviour

Correct Answer: A

CSIR-NET

Question: Black phosphorus is used in

1. match industry
2. high-performance lithium-ion batteries
3. smoke screens
4. rat poison

Correct Answer: B

Explanation: Emerging application in next-gen batteries and electronics.

JEE Advanced

Question: Which allotrope has the highest melting point?

1. White P (44°C)
2. Red P (590°C)
3. Black P (∼610°C under pressure)
4. All same

Correct Answer: C

JEE Advanced / GATE

Question: Which of the following is correct order of reactivity?

1. White > Red > Black
2. Black > Red > White
3. Red > White > Black
4. White = Red = Black

Correct Answer: A

Explanation: White (most strained) > Red > Black (most stable)

Must Read Black Phosphorus: Preparation, Properties, Structure, Uses

Related Topics
White Phosphorus
Red Phosphorus
Black Phosphorus
White Phosphorus PYQs MCQs
Red Phosphorus PYQs MCQs
Black Phosphorus PYQs MCQs