--- title: "Explosive characteristics; TNT preparation" subject: "Engineering Chemistry" chapter: 7 key: "semester_2/engineering_chemistry:tnt-characteristics" source: https://www.bctengineer.com/q/semester_2/engineering_chemistry/tnt-characteristics site: BCT Engineering --- # Explosive characteristics; TNT preparation Engineering Chemistry · Chapter 7: Explosives - Asked in: 2073 Bhadra, 2+2+1 marks - Video: [Lecture 814Topic- CHARACTERISTICS OF EXPLOSIVES](https://www.youtube.com/watch?v=Vk3VfsU5Qcw) — Chemistry Lectures By Prof. I. Z. Khan - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_2/engineering_chemistry/tnt-characteristics - Whole chapter: https://www.bctengineer.com/md/semester_2/engineering_chemistry/chapter-7 ## Question Write the important characteristics of explosives? Give the preparation and uses of TNT. Why does detonator required for the explosion of TNT? ## Short answer Good explosives are stable, safe to handle, easily initiated, have high detonation velocity and brisance, produce large gas volume with high heat, and are cheap. TNT is prepared by stepwise nitration of toluene with HNO₃/H₂SO₄ at increasing temperatures. It is used in shells, bombs, mining, and demolition. A detonator is required because TNT is insensitive and needs a strong shock wave to initiate detonation. ## Answer #### Characteristics of explosives Important characteristics of a good explosive: 1. Stable during storage, without decomposing over time. 2. Safe to handle: not too sensitive to shock, friction or heat. 3. Easily exploded by a detonator or proper initiation. 4. High velocity of detonation and brisance (shattering power). 5. Large volume of gas released per unit mass, with high heat of explosion. 6. Gives little smoke and no poisonous fumes (for use in mines). 7. Cheap, easy to make from available raw materials, and non-hygroscopic. #### Preparation of TNT (2,4,6-trinitrotoluene) TNT is made by the stepwise nitration of toluene with a mixture of conc. HNO₃ and conc. H₂SO₄ (H₂SO₄ is a dehydrating agent, giving NO₂⁺). Toluene itself is obtained from benzene by Friedel–Crafts methylation (benzene + CH₃Cl, anhydrous AlCl₃). ```text C₆H₆ + CH₃Cl --AlCl₃--> C₆H₅CH₃ + HCl (toluene) C₆H₅CH₃ --HNO₃/H₂SO₄, 30°C--> mononitrotoluene --HNO₃/H₂SO₄, 60°C--> dinitrotoluene --HNO₃/oleum, 100-110°C--> 2,4,6-trinitrotoluene ``` ```text Structure of TNT (ring carbons C1 to C6) CH₃ | .----C1---. O₂N--C2 C6--NO₂ | | C3 C5 '---C4----' | NO₂ ``` The product is washed with water and dilute sodium carbonate and recrystallised from alcohol. It is a pale yellow crystalline solid, m.p. 81 °C. Decomposition: 2C₇H₅N₃O₆ → 3N₂ + 5H₂O + 7CO + 7C #### Uses - Filling for shells, bombs, grenades, torpedoes and mines. - Mining, quarrying and demolition (alone or as amatol/ammonal mixtures). - Raw material for other explosives and dyes. #### Why a detonator is required TNT is very stable and insensitive to heat, shock and friction. If lit, it burns quietly with a sooty flame and does not explode. The activation energy for its explosive decomposition is high, so a strong shock wave is needed to start it. A **detonator** (containing a sensitive primary explosive such as lead azide or mercury fulminate) gives this initial shock, which starts the detonation of the whole mass. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. Which pair of properties is required of a good explosive? A. Very sensitive to shock and friction B. Hygroscopic and unstable C. Stable in storage and safe to handle, yet easily exploded by a detonator D. Low gas output and high smoke Answer: C. A good explosive must be stable and safe but readily initiated. (Key point: Stability and safety) 2. Which reagent mixture is used to nitrate toluene to make TNT, and what is the role of H2SO4? A. Dilute HNO3 + dilute H2SO4; H2SO4 acts as a reducing agent B. Conc. HNO3 + conc. H2SO4; H2SO4 is a dehydrating agent that helps give NO2+ C. Conc. HNO3 alone; H2SO4 is not needed D. Conc. HCl + conc. H2SO4; H2SO4 supplies the nitro group Answer: B. TNT is made by stepwise nitration of toluene with conc. HNO3 and conc. H2SO4; the sulfuric acid removes water and helps form NO2+. (Key point: Nitrating mixture) 3. Which is a use of TNT? A. Filling shells, bombs and mines and for mining and demolition B. Making soap and detergents C. Use as a propellant for slow burning in fireworks D. Use only as a detonator primary charge Answer: A. TNT is a secondary high explosive used in shells, bombs, mines, mining, quarrying and demolition. (Key point: Uses of TNT) 4. What does a detonator do for TNT? A. It supplies extra oxygen to TNT B. It cools TNT to stop it exploding C. Its primary explosive (lead azide or mercury fulminate) gives the strong initial shock that starts detonation of the whole mass D. It dissolves TNT so it can react Answer: C. A detonator contains a sensitive primary explosive whose shock wave overcomes the high activation energy and starts detonation. 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