--- title: "Explosive characteristics; TNT preparation and uses" subject: "Engineering Chemistry" chapter: 7 key: "semester_2/engineering_chemistry:explosive-characteristics-tnt" source: https://www.bctengineer.com/q/semester_2/engineering_chemistry/explosive-characteristics-tnt site: BCT Engineering --- # Explosive characteristics; TNT preparation and uses Engineering Chemistry · Chapter 7: Explosives - Asked in: 2070 Bhadra, 2+3 marks - Video: [How to Prepare TNT in laboratory and industrially](https://www.youtube.com/watch?v=jikSUAxUKuA) — Robert Science Academy - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_2/engineering_chemistry/explosive-characteristics-tnt - Whole chapter: https://www.bctengineer.com/md/semester_2/engineering_chemistry/chapter-7 ## Question List the important characteristics of explosives. Give the preparation and uses of trinitrotoluene (TNT). ## Short answer Good explosives are stable, safe, 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. ## 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. ## 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 performance features does a good explosive need? A. Low velocity and little gas B. High detonation velocity (brisance) and a large volume of gas with high heat of explosion C. High smoke and poisonous fumes D. Low heat released Answer: B. Brisance and a large gas volume with high heat give power. (Key point: Performance requirement) 3. Which reagent mixture is used to nitrate toluene to make TNT, and what is the role of H2SO4? A. Conc. HNO3 + conc. H2SO4; H2SO4 is a dehydrating agent that helps give NO2+ B. Dilute HNO3 + dilute H2SO4; H2SO4 acts as a reducing agent C. Conc. HNO3 alone; H2SO4 is not needed D. Conc. HCl + conc. H2SO4; H2SO4 supplies the nitro group Answer: A. 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) 4. 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. 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