--- title: "Explosive characteristics; GTN and TNT; applications" subject: "Engineering Chemistry" chapter: 7 key: "semester_2/engineering_chemistry:explosive-characteristics-gtn-tnt" source: https://www.bctengineer.com/q/semester_2/engineering_chemistry/explosive-characteristics-gtn-tnt site: BCT Engineering --- # Explosive characteristics; GTN and TNT; applications Engineering Chemistry · Chapter 7: Explosives - Asked in: 2067 Mangsir, 1+1.5+1.5+1 marks - 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-gtn-tnt - Whole chapter: https://www.bctengineer.com/md/semester_2/engineering_chemistry/chapter-7 ## Question What are characteristics of an explosive? Give the preparation of glycerol trinitrate (GTN) and trinitrotoluene (TNT). Point out the industrial applications of explosives. ## Short answer Good explosives are stable, safe, easily initiated, have high brisance, produce large gas volume, and are cheap. GTN is made by nitrating glycerol with HNO₃/H₂SO₄ below 15°C; TNT by stepwise nitration of toluene. Industrial applications include mining, quarrying, tunnelling, demolition, oil-well perforation, and metal forming. ## Answer #### Characteristics of an explosive 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 glycerol trinitrate (GTN, nitroglycerine, TNG) GTN is made by nitrating glycerol with a mixture of conc. HNO₃ and conc. H₂SO₄ (the sulfuric acid absorbs the water formed). The temperature is kept below 10–15 °C by cooling, as higher temperatures can cause explosion. ```text CH₂OH CH₂ONO₂ | | CHOH + 3HNO₃ --H₂SO₄--> CHONO₂ + 3H₂O | | CH₂OH CH₂ONO₂ ``` The oily layer of GTN is separated, washed with water and sodium carbonate solution and dried. It is a colourless to pale yellow oily liquid, very sensitive to shock, and explodes violently: 4C₃H₅(ONO₂)₃ → 12CO₂ + 10H₂O + 6N₂ + O₂ #### 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 #### Industrial applications of explosives Industrial applications: mining and quarrying, tunnelling, road, dam and canal construction, demolition of old structures, oil-well perforation, metal forming/welding by explosion, and making fireworks and safety fuses. ## 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. Low gas output and high smoke D. Stable in storage and safe to handle, yet easily exploded by a detonator Answer: D. A good explosive must be stable and safe but readily initiated. (Key point: Stability and safety) 2. Why is the nitration of glycerol kept below about 10-15 C by cooling? A. Higher temperatures can cause the product to explode B. The reaction does not occur above 15 C C. To increase the water produced D. To make glycerol solid Answer: A. GTN is very shock- and heat-sensitive, so cooling prevents a violent explosion during preparation. (Key point: Temperature control) 3. 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 alone; H2SO4 is not needed C. Conc. HNO3 + conc. H2SO4; H2SO4 is a dehydrating agent that helps give NO2+ D. Conc. HCl + conc. H2SO4; H2SO4 supplies the nitro group Answer: C. 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 an industrial application of explosives? A. Water purification B. Mining, quarrying, tunnelling, demolition and oil-well perforation C. Soap making D. Textile dyeing only Answer: B. Explosives are used in mining, construction and metal forming. (Key point: Industrial applications) ## Related in Engineering Chemistry - [Explosive characteristics; TNT preparation and uses](https://www.bctengineer.com/question.md?key=semester_2%2Fengineering_chemistry%3Aexplosive-characteristics-tnt) — Engineering Chemistry, chapter 7 - [Low explosives and uses; glycerol trinitrate](https://www.bctengineer.com/question.md?key=semester_2%2Fengineering_chemistry%3Alow-explosives-gtn) — Engineering Chemistry, chapter 7 - [Primary and low explosives; glycerol trinitrate](https://www.bctengineer.com/question.md?key=semester_2%2Fengineering_chemistry%3Aprimary-low-explosives-gtn) — Engineering Chemistry, chapter 7 - [Explosive characteristics; TNT preparation](https://www.bctengineer.com/question.md?key=semester_2%2Fengineering_chemistry%3Atnt-characteristics) — Engineering Chemistry, chapter 7 - [Low and high explosives; GTN preparation](https://www.bctengineer.com/question.md?key=semester_2%2Fengineering_chemistry%3Ahigh-low-gtn) — Engineering Chemistry, chapter 7, asked 2× - [High and low explosives; TNT preparation](https://www.bctengineer.com/question.md?key=semester_2%2Fengineering_chemistry%3Ahigh-low-explosives-tnt) — Engineering Chemistry, chapter 7, asked 3×