The Explosive Substances is part of Chemistry. Below are notes on 5 sub-topics, followed by practice MCQs from State PSC and UPSC papers.

Chemical composition and functional groups of energetic materials

  • Sodium Azide (NaN₃): Used in vehicle airbags; rapidly decomposes to release nitrogen gas (N₂) for inflation.
  • Explosives:
    • TNT (Trinitrotoluene): A high explosive.
    • TNG (Trinitroglycerin) / Nitroglycerin: Powerful explosive, derived from glycerol.
    • Potassium Chlorate (KClO₃): Strong oxidizing agent, used in explosives, pyrotechnics, and match heads.
  • Non-explosive (among common options):
    • Nitrochloroform (Chloropicrin): A chemical warfare agent (tear gas), not an explosive.
  • Mustard Gas: A chemical warfare agent; chemically 2,2'-dichlorodiethyl sulfide.
  • Glycerol: An alcohol (propane-1,2,3-triol), used as a precursor in the production of nitroglycerin (an explosive).

Definition and classification of explosive substances

  • Explosive substances undergo rapid chemical reactions, producing gas, heat, and pressure.
  • Classification:
  • Low Explosives (Deflagrating): Burn rapidly, producing a propelling effect. Example: Gunpowder.
  • High Explosives (Detonating): Decompose extremely rapidly (detonation), creating a powerful shockwave. Examples: TNT, Dynamite, Gelatine.
  • Gunpowder (Black Powder): Is a low explosive.
  • Gunpowder Composition: Potassium nitrate (saltpetre), powdered charcoal, and sulphur.
  • Modern gunpowder granules are typically coated with Graphite.
  • Graphite coating on gunpowder prevents the build-up of electrostatic charge, reducing the risk of accidental ignition.
  • Most explosions in mines occur due to the mixing of methane with air.

Nitroglycerin and dynamite: Preparation, properties, and stabilization

  • Nitroglycerin (Glycerol trinitrate; C₃H₅(ONO₂)₃): A heavy, colorless, oily, highly unstable explosive liquid.
  • Preparation of Nitroglycerin: Produced by the nitration of glycerol with a concentrated nitrating mixture (nitric acid and sulfuric acid).
  • Properties of Nitroglycerin: Extremely sensitive to shock, friction, and temperature changes, making it very dangerous in pure liquid form due to explosive decomposition.
  • Stabilization of Nitroglycerin: Achieved by adsorbing it onto an inert porous material (to form dynamite) or by mixing it with other compounds (e.g., nitrocellulose) in propellants.
  • Dynamite: Invented by Alfred Nobel in 1867 to make nitroglycerin safer for handling and transport.
  • Preparation of Dynamite: Formed by absorbing nitroglycerin into an inert, porous material like kieselguhr (diatomaceous earth), wood pulp, or sawdust.
  • Properties of Dynamite: Significantly less sensitive to shock and friction compared to pure nitroglycerin, making it a safer blasting explosive.
  • Stabilization of Dynamite: The absorption of nitroglycerin onto inert materials like kieselguhr reduces its sensitivity to shock and friction, effectively stabilizing it.
  • Explosives containing Nitroglycerin: Dynamite, Cordite (nitroglycerin, nitrocellulose, petroleum jelly), Blasting Gelatine (nitroglycerin, nitrocellulose).
  • Explosives NOT containing Nitroglycerin: Amatol (a mixture of TNT and ammonium nitrate).

Primary explosives: Synthesis and properties (e.g., lead azide, mercury fulminate)

  • Primary Explosives: Highly sensitive chemical compounds that readily detonate from minor stimuli like impact, friction, heat, or electrostatic discharge.
  • Function: Used as initiators (detonators) for less sensitive secondary (high) explosives.
  • Lead Azide (Pb(N₃)₂) :
    • Synthesis: Reacting aqueous solutions of sodium azide (NaN₃) with lead nitrate (Pb(NO₃)₂) or lead acetate.
    • Properties: Extremely sensitive to impact/friction; less sensitive to heat than mercury fulminate. Non-corrosive, stable when dry. High brisance.
    • Use: Primary detonator for high explosives; common in commercial and military blasting caps.
  • Mercury Fulminate (Hg(CNO)₂) :
    • Synthesis: Prepared by dissolving mercury in concentrated nitric acid, then adding ethanol.
    • Properties: Highly sensitive to impact, friction, and heat. Corrosive. Less powerful than lead azide.
    • Use: Historically used in percussion caps and blasting caps; largely replaced by lead azide.
  • Safety Match Ignition Principle: Involves friction-induced primary ignition.
    • Striking Surface: Contains red phosphorus, powdered glass, and binder.
    • Match Head: Contains potassium chlorate (oxidizer), antimony trisulfide (fuel), sulfur, and binder.
    • First Step on Striking: Friction converts a small amount of red phosphorus into highly reactive white phosphorus.
    • Subsequent Ignition: White phosphorus spontaneously ignites, providing heat to initiate the match head components.

Secondary explosives: TNT, RDX, PETN, HMX – synthesis and characteristics

  • Secondary Explosives: Require a primary explosive (detonator) to initiate their explosion; generally more stable than primary explosives.
  • TNT (Trinitrotoluene):
    • Full Name: Trinitrotoluene.
    • Characteristics: Creamy yellow, solid organic nitrogen compound. Considered a high-intensity explosive substance.
    • Synthesis: Primarily through the nitration of toluene.
  • RDX (Research Department eXplosive / Royal Demolition eXplosive):
    • Alternate Names: Cyclonite, Hexogen.
    • Chemical Name (as per MCQ): 1, 3, 5trinitro-1, 3, 5-triazine. (Commonly known as cyclotrimethylenetrinitramine or hexahydro-1,3,5-trinitro-1,3,5triazine).
    • Characteristics: White powder, very powerful explosive.
    • Synthesis: Nitration of hexamine (hexamethylenetetramine).
  • PETN (Pentaerythritol Tetranitrate):
    • Full Name: Pentaerythritol Tetranitrate.
    • Characteristics: Very powerful and highly sensitive secondary explosive.
    • Synthesis: Nitration of pentaerythritol.
  • HMX (High Melting eXplosive / HighVelocity eXplosive):
    • Alternate Name: Octogen.
    • Chemical Name: Cyclotetramethylenetetranitramine.
    • Characteristics: More powerful and thermally stable than RDX. Possesses high density and high detonation velocity.
    • Synthesis: Can be produced by the nitration of hexamine or from RDX as an intermediate.
  • Other Explosive Substances Mentioned:
    • Nitrocellulose: An explosive.
    • Gunpowder: Composed of Sulphur, Charcoal, and Potassium nitrate (Barium sulphate is NOT present).
    • TNG: Trinitroglycerin (Nitroglycerin), an explosive.
  • Non-explosive Substances Mentioned:
    • Kevlar: A synthetic fibre.
    • Taxol: An anticancer drug.
    • Zinc Phosphide: A rodenticide.
    • CNG: Compressed Natural Gas (a fuel).

17. The Fuel

Practice MCQs: The Explosive Substances

Chemical composition and functional groups of energetic materials

  1. The chemical used in airbags of vehicles that releases nitrogen to explode balloons in case of accidents is A) Sodium azide B) Sodium nitrite C) Silver nitrate D) Potassium nitrate

    Asked in: TSPSC Group 1 Prelims 2023

    1. Sodium azide
    2. Sodium nitrite
    3. Silver nitrate
    4. Potassium nitrate
    Show answer

    Answer: A. Sodium azide

    Automobile airbags typically contain sodium azide (NaN₃). In the event of a crash, an impact sensor triggers a chemical reaction. Electrical current ignites a small charge, which decomposes the sodium azide into sodium metal and a large volume of nitrogen gas (2 NaN₃ → 2 Na + 3 N₂). This rapid production of nitrogen gas inflates the airbag very quickly.

  2. Which one of the following is not an explosive?

    Asked in: UPPSC Upper Mains 2015 · TOURIST INFORMATION OFFICER(TIO) 2017

    1. Nitrochloroform
    2. TNG
    3. TNT
    4. Potassium chlorate
    Show answer

    Answer: A. Nitrochloroform

    Nitrochloroform, also known as Chloropicrin (CCl3NO2), is primarily known for its use as a D. Carbon tetrachloride Ans: B Vinegar is the trade name for a dilute aqueous solution of acetic acid. fumigant, insecticide, and a tear gas (lachrymator). While it can be toxic and hazardous, it is not classified or primarily used as a high explosive in the same category as TNG or TNT.

  3. Mustard Gas is :

    Asked in: opsc 2025 2025

    1. Uranium hexafluoride
    2. Dichlorodiphenyltrichloroethane
    3. 2,2'-dichlorodiethylsulfide
    4. Diethylsulphoxide
    Show answer

    Answer: C. 2,2'-dichlorodiethylsulfide

    Mustard Gas is chemically identified as 2,2'-dichlorodiethylsulfide.

  4. Oxidant used in the manufacture of match sticks is

    Asked in: Assistant Engineer (AE) Exam 2012

    1. Potassium dichromate
    2. Potassium permanganate
    3. Potassium nitrate
    4. Nitric acid
    Show answer

    Answer: A. Potassium dichromate

    Oxidizing agents are crucial components in the ignition mechanism of matchsticks, facilitating the combustion process.

  5. Which one of the following is used in production of explosives ?

    Asked in: RO ARO pre 2016

    1. Glycerol
    2. Methanol
    3. Urea
    4. Oxalic acid
    Show answer

    Answer: A. Glycerol

    Certain organic compounds serve as precursors for the synthesis of explosives.

Definition and classification of explosive substances

  1. Gun powder is a mixture which when ignited a number of chemical reactions take place producing explosion. It consists of : (a) Potassium nitrate (b) Powdered charcoal (c) Sulphur (d) Sodium Carbonate (e) Calcium Sulphate

    Asked in: MPSC CS Prelims 2013

    1. (a), (b), (c)
    2. (b), (c), (d)
    3. (a), (b), (e)
    4. (a), (c), (d)
    Show answer

    Answer: A. (a), (b), (c)

    - Gunpowder is a mixture of an oxidizer, a fuel, and a stabilizer. - The traditional components are potassium nitrate, charcoal, and sulphur.

  2. Statement-I: The granules of modern gunpowder (also called black powder) are typically coated with Graphite. Statement-II: Graphite prevents the build-up of electrostatic charge.

    Asked in: UPSC NDA 1 2015

    1. Both the statements are individually true and Statement II is the correct explanation of Statement I
    2. Both the statements are individually true but Statement II is not the correct explanation of Statement I
    3. Statement I is true but Statement II is false
    4. Statement I is false but Statement II is true
    Show answer

    Answer: A. Both the statements are individually true and Statement II is the correct explanation of Statement I

    Statement I is true; graphite is commonly used as a coating for black powder granules. Statement II is also true; graphite is a good conductor and helps dissipate electrostatic charge.

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

    Asked in: UPSC NDA 1 2015

    1. Magnesium sulphate
    2. Potassium nitrate
    3. Sodium stearate
    4. Calcium sulphate
    Show answer

    Answer: B. Potassium nitrate

    Gunpowder is typically a mixture of potassium nitrate (oxidizer), charcoal (fuel), and sulfur (fuel/ stabilizer). Potassium nitrate serves as the oxidizer, providing oxygen for the rapid combustion of the fuel components.

  4. Which one of the following is an example of low explosive?

    Asked in: UPSC CISF AC EXE 2021

    1. Gunpowder
    2. Gelatine
    3. TNT
    4. Dynamite
    Show answer

    Answer: A. Gunpowder

    Low explosives deflagrate, while high explosives detonate.

  5. Most of the explosions in mines occur due to the mixing of

    Asked in: UPPCS Prelims 2000

    1. hydrogen with oxygen
    2. oxygen with acetylene
    3. methane with air
    4. carbon dioxide with ethane
    Show answer

    Answer: C. methane with air

    Coal mines often contain pockets of methane gas (CH4), also known as "firedamp". When methane mixes with air in certain proportions (typically 5-15% methane), it forms a highly explosive mixture. Sparks from machinery, electrical equipment, or smoking can ignite this mixture, causing violent explosions.

Nitroglycerin and dynamite: Preparation, properties, and stabilization

  1. The chemical used in manufacturing of dynamite is

    Asked in: JPSC CS Prelims 2016

    1. Glycerol
    2. Glycerol triacetate
    3. Glycerol trinitrate
    4. Glycerol triiodate
    Show answer

    Answer: C. Glycerol trinitrate

    Dynamite, invented by Alfred Nobel, primarily consists of nitroglycerin absorbed into a stable material like sawdust, diatomaceous earth, or plastic pellets. Nitroglycerin is chemically known as Glycerol trinitrate, an explosive liquid.

  2. Match List-I with List-II and select the correct answer using the codes given below : List-I List-II

    Asked in: UPPSC Upper Mains 2010

    1. Alfred Nobel 1. Theory of Evolution
    2. Alexander Fleming 2. Dynamite
    3. Charles Darwin 3. Penicillin
    4. Madame Curie 4. Isolation of radium Code: A. A-1, B-2, C-3, D-4 B. A-2, B-3, C-1, D-4 C. A-3, B-2, C-1, D-4 D. A-1, B-4, C-3, D-2
    Show answer

    Answer: B. Alexander Fleming 2. Dynamite

    Matching prominent scientists/inventors with their key contributions.

  3. Which one of the following explosives does not contain nitroglycerine as an essential constituent?

    Asked in: UPPSC Upper Mains 2010

    1. Cordite
    2. Blasting Gelatine
    3. Dynamite
    4. Amatol
    Show answer

    Answer: D. Amatol

    Identify the primary components of common explosives.

  4. Which one of the following was invented by Alfred Nobel?

    Asked in: Group B Exam 2012

    1. Aeroplane
    2. Telephone
    3. Safety lamp
    4. Dynamite
    Show answer

    Answer: D. Dynamite

    This question is a direct recall of a famous inventor and his most significant invention.

Primary explosives: Synthesis and properties (e.g., lead azide, mercury fulminate)

  1. When one strikes a safety match, the first step is

    Asked in: UPSC NDA 2 2016

    1. burning of sulfur
    2. decomposition of potassium chlorate into potassium chloride and oxygen
    3. conversion of a small amount of red phosphor‐ us into white phosphorus
    4. burning of glue and starch
    Show answer

    Answer: C. conversion of a small amount of red phosphor‐ us into white phosphorus

    A safety match head contains oxidizer (like KClO₃), fuel (sulfur), and binder. The striking surface contains red phosphorus, glass powder, and binder. Striking the head against the surface creates friction, which generates heat. This heat energy is sufficient to convert a tiny amount of red phosphorus on the strip into the highly reactive white phosphorus, which ignites instantly in air. This initial ignition then provides the heat to decompose the potassium chlorate in the match head, releasing oxygen, which oxidizes the sulfur, causing the main flame.

Secondary explosives: TNT, RDX, PETN, HMX – synthesis and characteristics

  1. Which of the following statements is/are correct regarding RDX? RDX stands for Royal Demolition eXplosive and Research Department eXplosive It is also known as cyclonite or hexogen. The chemical name for RDX is 1, 3, 5- trinitro-1, 3, 5-triazine. It is a white powder and is very explosive.

    Asked in: GPSC Prelims CSP 2 2021

    1. 1, 2 and 3
    2. 2 and 3 only
    3. 1 and 2 only
    4. 2 only
    Show answer

    Answer: B. 2 and 3 only

    - RDX has common names like cyclonite and hexogen. - Its chemical name is related to trinitrotriazine. - It is a powerful high explosive. - The etymology of the acronym RDX has debated origins.

  2. Match List-I with List-II and select the correct answer from the codes given below the lists: List-I List-II

    Asked in: UPPCS Prelims 2019

    1. Kevlar 1. Explosive
    2. Taxol 2. Synthetic fibre
    3. Zinc Phosphide 3. Anticancer drug
    4. Nitrocellulose 4. Rodenticide Codes: A. A B C D (a) 2 4 3 1 B. A B C D (b) 2 3 4 1 C. A B C D (c) 4 3 1 2 D. A B C D (d) 3 1 2 4
    Show answer

    Answer: B. Taxol 2. Synthetic fibre

    Let's match the items: A. Kevlar: This is a high- strength synthetic fiber used in applications like bulletproof vests, aramid ropes, and bicycle tires. It matches with 2. Synthetic fibre. B. Taxol (Paclitaxel): This is a widely used chemotherapy drug used to treat various types of cancer. It matches with 3. Anticancer drug. C. Zinc Phosphide: This inorganic compound is commonly used as a rodenticide (poison to kill rodents). It matches with 4. Rodenticide. D. Nitrocellulose: Also known as cellulose nitrate, it is highly flammable and used in explosives (like guncotton), propellants, lacquers, and films. It matches with 1. Explosive. Thus, the correct mapping is A-2, B-3, C-4, D-1. This matches option (b).

  3. Which one of the following materials is not present in gun powder?

    Asked in: UPSC CISF AC EXE 2017

    1. Sulphur
    2. Charcoal
    3. Potassium nitrate
    4. Barium sulphate
    Show answer

    Answer: D. Barium sulphate

    Traditional black gunpowder consists of a mixture of three main components: Potassium nitrate (KNO₃), Charcoal (primarily carbon), and Sulphur (S).

  4. What is PETN?

    Asked in: UPSC CISF AC EXE 2019

    1. Pentane epinephirine tantalum nitro
    2. Pentaerythritol tetranitrate
    3. Phenol erythritol tetranitrate
    4. None of the above
    Show answer

    Answer: B. Pentaerythritol tetranitrate

    PETN is a powerful explosive, known for its high brisance and sensitivity to initiation, making it commonly used in detonators, booster charges, and plastic explosives.

  5. What does TNT stand for ?

    Asked in: UPSC CISF AC EXE 2020

    1. Tri Nitro Toluene
    2. Tri Nitro Tartum
    3. Tetra Nitro Toluene
    4. Thallium Nitrate Tetryl
    Show answer

    Answer: A. Tri Nitro Toluene

    Tri Nitro Toluene (TNT) is a chemical compound with the formula C₆H₂ (NO₂)₃CH₃. It is a highly stable explosive material and one of the most widely used explosives, particularly in military and mining applications.

  6. Which one of the following statements with regard to TNT is not correct ?

    Asked in: UPSC CISF AC EXE 2023

    1. TNT stands for trinitrotoluene
    2. It is of creamy yellow colour
    3. It is a solid organic nitrogen compound
    4. It is considered to be a low intensity explosive substance
    Show answer

    Answer: D. It is considered to be a low intensity explosive substance